An inorganic magnesium salt electrolyte for rechargeable magnesium batteries and a preparation method and application thereof

Abstract

The application discloses a rechargeable magnesium battery inorganic magnesium salt electrolyte and a preparation method and application thereof, and belongs to the technical field of new energy battery preparation. The rechargeable magnesium battery inorganic magnesium salt electrolyte comprises an electrolyte salt inorganic magnesium salt, an organic ether solvent and an electrolyte additive organic phosphorus molecule. The application introduces the organic phosphorus molecule with high dielectric constant into the inorganic magnesium salt electrolyte, optimizes and controls the solvation structure of magnesium ions in the electrolyte and the solubility of the electrolyte itself, forms a stable magnesium ion solid-state electrolyte conductive layer on the surface of the magnesium metal, improves the magnesium ion conductivity, and reduces the side reaction between the magnesium negative electrode and the electrolyte. Meanwhile, the electrochemical polarization energy barrier of the electrolyte is reduced, and the reversibility and oxidation stability of the rechargeable magnesium battery are improved. The electrolyte only needs to be prepared by stirring the single inorganic magnesium salt and the organic phosphorus additive in the ether solvent, does not need additional additives and water removing agents, and has the advantages of simple preparation method and easy large-scale production.

Description

Technical Field

[0001] This invention relates to the field of new energy battery preparation technology, specifically to an inorganic magnesium salt electrolyte for rechargeable magnesium batteries, its preparation method, and its application. Background Technology

[0002] Rechargeable lithium-ion batteries have revolutionized the mobile device industry and are gaining increasing attention in the development of electric vehicles and grid storage applications. However, due to the scarcity and high cost of lithium resources, there is a need to explore more sustainable battery materials. Rechargeable magnesium batteries stand out because metallic magnesium, acting as the negative electrode, exhibits minimal dendrite formation on its surface during charging and discharging. Furthermore, metallic magnesium possesses a low reduction potential (-2.37V vs. standard hydrogen electrode) while demonstrating a high theoretical specific capacity (2205 mAh g⁻¹). -1 ) and volumetric capacity (3833mAh cm⁻¹) -3 ), and is more abundant in the Earth's crust (magnesium 1.94%, lithium 0.002%). Therefore, divalent Mg is used. 2+ Replacement of monovalent ions (Li + Na + This can enable rechargeable batteries with high energy density.

[0003] However, the lack of a suitable electrolyte remains a key challenge in constructing high-energy-density rechargeable magnesium batteries. The electrolyte, as a Mg... 2+ The transport medium determines not only the compatibility with the electrodes but also the electrochemical, thermodynamic, and safety stability of the battery energy storage system. In traditional magnesium battery electrolytes, the Mg surface is easily and severely passivated, hindering the dissolution-deposition process of magnesium ions, resulting in slow kinetics and ultra-high overpotentials. There are relatively few traditional electrolytes that simultaneously meet a wide electrochemical window and can reversibly dissolve and deposit magnesium metal.

[0004] In conclusion, these challenges have significantly hampered the development of rechargeable magnesium-ion batteries. Summary of the Invention

[0005] Purpose of the Invention: To address the problems of poor solubility, low oxidation stability, poor high-current resistance, complex preparation process, and high cost of existing magnesium battery electrolytes, the first objective of this invention is to provide an inorganic magnesium salt electrolyte for rechargeable magnesium batteries with high ionic conductivity and high magnesium metal dissolution-deposition efficiency. The second objective of this invention is to provide a method for preparing the above-mentioned inorganic magnesium salt electrolyte for rechargeable magnesium batteries. The third objective of this invention is to provide applications of the above-mentioned inorganic magnesium salt electrolyte for rechargeable magnesium batteries.

[0006] Technical solution: The inorganic magnesium salt electrolyte for rechargeable magnesium batteries of the present invention includes an electrolyte salt, an organic ether solvent and an electrolyte additive; the electrolyte salt is an inorganic magnesium salt, the electrolyte additive is an organic phosphorus molecule, and the volume fraction of the organic phosphorus molecule in the electrolyte is 5-40%, preferably 20-40%.

[0007] Furthermore, the inorganic magnesium salt is magnesium chloride. Magnesium chloride mainly serves as the source of magnesium ions in the electrolyte. Compared with other common magnesium salts, it has higher conductivity and better magnesium metal dissolution and deposition efficiency. At the same time, it is low in cost, simple in synthesis steps, and not easily affected by trace amounts of moisture, making it an ideal electrolyte salt.

[0008] Further, the organic ether solvent is one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxane and 1,4-dioxane, preferably tetrahydrofuran or ethylene glycol dimethyl ether.

[0009] Furthermore, the organophosphorus molecule is at least one of trimethyl phosphate, triethyl phosphate, dibutyl phosphate, and trimethyl phosphite, preferably trimethyl phosphate or triethyl phosphate.

[0010] Furthermore, the molar concentration of the electrolyte salt in the electrolyte is 0.1-1.0 mol / L, preferably 0.25-0.5 mol / L.

[0011] This invention provides a method for preparing the above-mentioned inorganic magnesium salt electrolyte for rechargeable magnesium batteries, comprising the following steps:

[0012] (1) Add inorganic magnesium salt to an organic ether solvent and stir to dissolve and disperse it to obtain a reaction solution;

[0013] (2) Add electrolyte additives to the above reaction solution and continue stirring. After thorough mixing, the inorganic magnesium salt electrolyte for rechargeable magnesium batteries is obtained.

[0014] Further, steps (1) and (2) are carried out in an argon glove box with water and oxygen content both below 0.1 ppm; the organic ether solvent and electrolyte additive are pre-treated by molecular sieve drying; the stirring conditions are: stirring temperature of 40-90℃, stirring speed of 300-1000 r / min, and stirring time of 10-20 min.

[0015] This invention provides the application of inorganic magnesium salt electrolyte for rechargeable magnesium batteries in symmetrical and asymmetrical magnesium-ion batteries.

[0016] Furthermore, the symmetrical battery includes a positive electrode material, a negative electrode material, a separator, and a rechargeable magnesium battery composite electrolyte, wherein the positive electrode material is metallic magnesium or a magnesium alloy; the asymmetric battery includes a positive electrode material, a negative electrode material, a separator, and a rechargeable magnesium battery electrolyte, wherein the positive electrode material is aluminum, copper, molybdenum, stainless steel, titanium, or zinc.

[0017] Furthermore, the negative electrode material of both the symmetrical and asymmetric batteries is metallic magnesium or magnesium alloy, and the separator is at least one of glass fiber separator, polyethylene membrane, polypropylene membrane or polymer composite membrane.

[0018] Invention principle: In the inorganic magnesium salt electrolyte of the rechargeable magnesium battery of the present invention, the following interactions exist:

[0019] 1. Interactions between organophosphorus electrolyte additives and ether solvents: Organophosphorus molecules and ether solvents exhibit strong interactions at the molecular level. Due to their high dielectric constant, organophosphorus molecules can synergistically interact with the polar portions of solvent molecules, thereby altering the solvation structure of magnesium ions. This interaction helps increase the solubility of magnesium ions in the solvent, making them more readily migrate to the electrode surface and improving the electrolyte conductivity. Especially under high load current conditions, the increased electrolyte conductivity reduces overpotential, thus improving battery performance.

[0020] 2. Interaction between organophosphorus molecules and inorganic magnesium salts in electrolyte additives: Inorganic magnesium salts typically form dimer cationic complexes (such as [Mg2(μ-Cl)3·solvent]+) in solvents, which are the active substances in the electrolyte. Under the influence of organophosphorus molecules, the stability of these complexes can be regulated, thereby altering the solvation structure of magnesium ions in the electrolyte and promoting the dissolution of magnesium ions and the electrode deposition process.

[0021] 3. Interaction between electrolyte additives (organophosphorus molecules) and the electrode surface: During battery operation, organophosphorus molecules interact with the magnesium metal anode surface, promoting the formation of a stable solid electrolyte conductive layer. This layer not only helps improve the deposition efficiency of magnesium ions but also reduces adverse reactions between the electrolyte and the metal anode (such as the formation of a passivation film), thereby maintaining the battery's high cycle performance. This solid electrolyte conductive layer plays an important buffering role during battery charging and discharging, mitigating side reactions between the electrolyte and the anode, and improving the overall stability and oxidation stability of the battery.

[0022] 4. The effect of organophosphorus additives on electrolyte electrochemical polarization: The addition of organophosphorus molecules reduces the electrochemical polarization energy barrier of the electrolyte during battery charging and discharging. This effect helps to improve the deposition-dissolution efficiency of magnesium metal, while reducing the battery overpotential, especially at high current densities.

[0023] In summary, the role of organophosphorus molecules in the electrolyte of this invention is not limited to improving the electrolyte's conductivity and reducing overpotential, but also includes interactions with other solvents (such as ether solvents), enhancing the electrolyte's stability and electrochemical performance. Through these interactions, organophosphorus molecules help increase the solubility of magnesium ions, promote the deposition-dissolution process of magnesium metal, reduce side reactions and passivation film formation in the electrolyte, thereby ensuring the battery's high performance and long-cycle stability.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention uses magnesium chloride as a single magnesium salt and organic phosphorus molecules as a single component additive to dissolve and prepare electrolyte, without the need for additional additives and dehydrating agents, solving the solubility problem of magnesium chloride in ether solvents, greatly reducing the production process cost, facilitating large-scale production, while improving electrochemical performance and reducing the electrochemical polarization of the electrolyte itself, thereby improving the reversibility and oxidation stability of rechargeable magnesium batteries. Attached Figure Description

[0025] Figure 1 Photographs of the electrolytes prepared in Examples 1-10 and Comparative Examples 1-3;

[0026] Figure 2 This is a comparison chart of the conductivity of the electrolytes prepared in Examples 1-5 and Comparative Example 2;

[0027] Figure 3 The graphs show the charge-discharge curves of the electrolytes prepared in Examples 1-5 and Comparative Example 2 in a Mg||Mg symmetric cell, with a current density of 0.1 mA cm⁻¹. -2 The surface area capacity is 0.05mAh cm⁻¹ -2 ;

[0028] Figure 4 The above are charge-discharge curves of the electrolytes prepared in Examples 4, 6-8, and 8 in a Mg||Mg symmetric cell (where the current density in Example 4 is 0.5 mA cm⁻¹). -2 The surface area capacity is 0.25mAh cm⁻¹ -2 In Examples 6-8, the current density was 0.1 mA cm⁻¹. -2 The surface area capacity is 0.05mAh cm⁻¹ -2 );

[0029] Figure 5 The figures show the rate performance curves of the electrolytes prepared in Examples 1-5 and Examples 7-8 in Mg||Mg symmetric cells at different current densities. The current density test range is 0.05 mA cm⁻¹. -2 Up to 6mA cm -2The surface area capacity is 0.2 mAh cm⁻¹ -2 ;

[0030] Figure 6 The graphs show the charge-discharge curves of the electrolytes prepared in Examples 9-10 and Comparative Example 3 in a Mg||Mg symmetric cell, with a current density of 0.1 mA cm⁻¹. -2 The surface area capacity is 0.05mAh cm⁻¹ -2 ;

[0031] Figure 7 The graphs show the rate performance curves of the electrolytes prepared in Examples 9-10 and Comparative Example 3 in Mg||Mg symmetric cells at different current densities. The current density test range is 0.05 mA cm⁻¹. -2 Up to 6mA cm -2 The surface area capacity is 0.2 mAh cm⁻¹ -2 ;

[0032] Figure 8 The figures show the electrochemical impedance spectroscopy (EIS) diagrams of the electrolytes prepared in Examples 1-5 before and after cycling in a Mg||Mg symmetric cell, with a test range of 10. 6 Hz to 10 -2 Hz, amplitude of 5mV;

[0033] Figure 9 Linear sweep voltammetry (LSV) plots of the electrolytes prepared in Examples 1-5 for asymmetric cells composed of different research electrodes and magnesium electrodes are shown. The voltage sweep range is from open-circuit voltage (OCV) to 6.5 V, and the sweep rate is 5 mV / s. -1 ;

[0034] Figure 10 The figures show the charge-discharge curves and coulombic efficiency of the electrolyte prepared in Example 4 in asymmetric cells composed of different research electrodes (SS, Ti) and magnesium electrodes, with a current density of 0.05 mA cm⁻¹. -2 The surface area capacity is 0.025mAh cm⁻¹. -2 ;

[0035] Figure 11 The X-ray diffraction (XRD) patterns of the electrolytes prepared in Examples 1-5 after cycling in a Mg||Mg symmetric cell;

[0036] Figure 12 Scanning electron microscope (SEM) images of the electrolytes prepared in Examples 1-5 after electrochemical testing of magnesium metal dissolution / deposition (where a is Example 1, b is Example 2, c is Example 3, d is Example 4, and e is Example 5).

[0037] Figure 13Fourier transform infrared (FTIR) spectra of the electrolytes prepared in Examples 4, 10, and 2 (which also include the infrared spectra of each individual solvent (THF, DME, TEP)). Detailed Implementation

[0038] The present invention will now be further described in conjunction with specific embodiments and accompanying drawings.

[0039] In the following examples, battery performance tests were conducted using the Blue Battery Testing System and the Chenhua Electrochemical Workstation, and physical property characterization was performed using scanning electron microscopy and X-ray diffraction. To test the electrochemical performance of the electrolyte, Mg||Mg symmetric and asymmetric cells (containing Mg||Al, Mg||Cu, Mg||Mo, Mg||SS, and Mg||Ti) were used, employing the electrolyte prepared in the following examples. Glass fiber was used as the separator, and CR2032 button cells were assembled for magnesium metal dissolution / deposition, electrochemical impedance spectroscopy, and linear sweep voltammetry tests.

[0040] Example 1: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 95:5, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0041] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed in an argon glove box with both water and oxygen content below 0.1 ppm and added to 4.75 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 0.25 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to 5%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-DME-5% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0042] Example 2: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 90:10, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0043] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 4.5 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 0.5 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to be 10%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-DME-10% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0044] Example 3: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 80:20, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0045] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 4 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 1 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to be 20%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-DME-20% TEP electrolyte. Before use, an appropriate amount of [unspecified substance] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0046] Example 4: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 70:30, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0047] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed in an argon glove box with both water and oxygen content below 0.1 ppm and added to 3.5 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 1.5 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to 30%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-DME-30% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0048] Example 5: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 60:40, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0049] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 3 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45°C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 2 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to 40%. The mixture is then magnetically stirred at 600 r / min at 45°C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-DME-40% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0050] Example 6: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and trimethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to trimethyl phosphate is 70:30, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0051] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 3.5 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 1.5 mL of trimethyl phosphate (TMP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TMP volume ratio to 30%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-DME-30% TMP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0052] Example 7: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 80:20, and the molar concentration of magnesium chloride in the electrolyte is 0.5 mol / L.

[0053] The preparation method of the above electrolyte includes the following steps: 0.238 g of anhydrous magnesium chloride is weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 4 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 1 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to be 20%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.5 mol / L (M) MgCl2-DME-20% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0054] Example 8: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, ethylene glycol dimethyl ether as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of ethylene glycol dimethyl ether to triethyl phosphate is 70:30, and the molar concentration of magnesium chloride in the electrolyte is 0.5 mol / L.

[0055] The preparation method of the above electrolyte includes the following steps: 0.238 g of anhydrous magnesium chloride is weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 3.5 mL of ethylene glycol dimethyl ether solvent. The mixture is magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the ethylene glycol dimethyl ether, yielding a MgCl2-DME blank electrolyte. Subsequently, 1.5 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-DME blank electrolyte, controlling the TEP volume ratio to 30%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.5 mol / L (M) MgCl2-DME-30% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0056] Example 9: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, tetrahydrofuran as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of tetrahydrofuran to triethyl phosphate is 80:20, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0057] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed into 4 mL of tetrahydrofuran solvent in an argon glove box with both water and oxygen content below 0.1 ppm. The mixture is then magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the tetrahydrofuran, yielding a MgCl2-THF blank electrolyte. Subsequently, 1 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-THF blank electrolyte, controlling the TEP volume ratio to 20%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-THF-20% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0058] Example 10: The inorganic magnesium salt electrolyte for the rechargeable magnesium battery provided in this example includes magnesium chloride as an electrolyte salt, tetrahydrofuran as an organic solvent, and triethyl phosphate as an electrolyte additive. The volume ratio of tetrahydrofuran to triethyl phosphate is 70:30, and the molar concentration of magnesium chloride in the electrolyte is 0.25 mol / L.

[0059] The preparation method of the above electrolyte includes the following steps: 0.119 g of anhydrous magnesium chloride is weighed into 3.5 mL of tetrahydrofuran solvent in an argon glove box with water and oxygen content both below 0.1 ppm. The mixture is then magnetically stirred at 600 r / min at 45 °C for 15 minutes to ensure uniform dispersion of magnesium chloride in the tetrahydrofuran, yielding a MgCl2-THF blank electrolyte. Subsequently, 1.5 mL of triethyl phosphate (TEP) is pipetted into the MgCl2-THF blank electrolyte, controlling the TEP volume ratio to 30%. The mixture is then magnetically stirred at 600 r / min at 45 °C for 30 minutes. After sufficient reaction, a colorless, clear, and transparent composite electrolyte is obtained, namely, 0.25 mol / L (M) MgCl2-THF-30% TEP electrolyte. Before use, an appropriate amount of [unspecified ingredient] is added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0060] Comparative Example 1: The electrolyte provided in this comparative example was prepared as follows: 0.119 g of anhydrous magnesium chloride was weighed in an argon glove box with water and oxygen content both below 0.1 ppm and added to 5 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at a stirring speed of 600 r / min and the temperature was maintained at 45 °C for 30 minutes to ensure that magnesium chloride was uniformly dispersed in ethylene glycol dimethyl ether to form a milky white turbid liquid with suspended particles, thus obtaining a blank saturated electrolyte of 0.25 mol / L (M) MgCl2-DME.

[0061] Comparative Example 2: The electrolyte provided in this comparative example was prepared as follows: 0.119 g of anhydrous magnesium chloride was weighed into 5 mL of triethyl phosphate (TEP) solvent in an argon glove box with both water and oxygen content below 0.1 ppm. The mixture was then magnetically stirred at 600 r / min at 45 °C for 30 minutes to ensure uniform dispersion and dissolution of magnesium chloride in the triethyl phosphate, resulting in a clear and transparent 0.25 mol / L (M) MgCl2-TEP electrolyte. Before use, an appropriate amount of [unspecified substance] was added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0062] Comparative Example 3: The electrolyte provided in this comparative example was prepared as follows: 0.119 g of anhydrous magnesium chloride was weighed into 5 mL of tetrahydrofuran (THF) solvent in an argon glove box with both water and oxygen content below 0.1 ppm. The mixture was then magnetically stirred at 600 r / min at 45 °C for 60 minutes to ensure uniform dispersion and dissolution of magnesium chloride in the tetrahydrofuran, resulting in a clear and transparent blank electrolyte of 0.25 mol / L (M) MgCl2-THF. Before use, an appropriate amount of [unspecified substance] was added to the electrolyte. Molecular sieves were dried overnight. The electrolyte moisture content was tested and found to be below 10 ppm.

[0063] The electrolytes prepared in Examples 1-10 and Comparative Examples 1-3 were characterized and their performance was tested. The results are shown in the figure. Figures 1-13 .

[0064] Figure 1 Photographs of the electrolytes prepared in Examples 1-10 and Comparative Examples 1-3 are shown (where a is Comparative Example 1, b is Example 1, c is Example 2, d is Example 3, e is Example 4, f is Example 5, g is Comparative Example 2, h is Example 6, i is Example 7, j is Example 8, k is Comparative Example 3, l is Example 9, and m is Example 10). The test results show that inorganic magnesium chloride salts can dissolve in the cyclic ether solvent tetrahydrofuran (THF), but adding different concentrations of triethyl phosphate can accelerate dissolution and yield a clear electrolyte more quickly. However, inorganic magnesium chloride salts have poor solubility in the chain ether solvent dimethyl glycol ether (DME). Adding different concentrations of triethyl phosphate (TEP) or trimethyl phosphate (TMP) can solve the solubility problem of inorganic magnesium chloride salts in chain ether solvents. Since anhydrous magnesium chloride has poor solubility in single ether solvents, Comparative Example 1 was not further investigated.

[0065] Figure 2 The graph shows a comparison of the conductivity of the electrolytes prepared in Examples 1-5 and Comparative Example 2. The test results show that the conductivity of the electrolyte with different concentrations of triethyl phosphate added to the 0.25M (mol / L) MgCl2-DME electrolyte continuously increases until it reaches the 30% inflection point, after which the conductivity begins to decrease. This indicates that 30% triethyl phosphate is the optimal concentration ratio in the MgCl2-DME electrolyte, and the addition of 30% triethyl phosphate greatly promotes the magnesium ion migration kinetics.

[0066] Figure 3 The charge-discharge curves and cycle stability of the magnesium anodes prepared in Examples 1-5 and Comparative Example 2 are shown in their respective electrolytes (where a is Example 1, b is Example 2, c is Example 3, d is Example 4, e is Example 5, and f is Comparative Example 2). The test results demonstrate the charge-discharge performance of electrolytes with different concentrations of triethyl phosphate added to 0.25 M (mol / L) MgCl2-DME electrolyte in a Mg||Mg symmetric battery, with a constant current charge-discharge current density of 0.1 mA / cm². -2 Constant capacity 0.05mAh cm -2The addition of triethyl phosphate significantly reduced the overpotential for magnesium metal dissolution / deposition and greatly promoted interfacial charge-mass transfer kinetics, indicating that this type of electrolyte has excellent electrochemical performance as a magnesium metal anode. However, due to the poor electrochemical performance of inorganic magnesium chloride in 100% triethyl phosphate solvent, no further in-depth research was conducted.

[0067] Figure 4 The charge-discharge curves and cycle stability of the magnesium anodes prepared in Examples 4, 6-8, and 8 are shown in the corresponding electrolytes (where a is Example 4, b is Example 6, c is Example 7, and d is Example 8). The test results demonstrate the charge-discharge performance of an electrolyte containing 30% triethyl phosphate in a 0.25 M (mol / L) MgCl2-DME electrolyte in a Mg||Mg symmetric cell, with a constant current charge-discharge current density of 0.5 mA / cm². -2 Constant capacity 0.25mAh cm -2 Even with a five-fold increase in current density, the symmetrical cell exhibits a low overpotential (less than 0.5V) and maintains cycling performance exceeding 800 hours, indicating that this concentration provides superior electrochemical performance for the magnesium metal anode. The study also demonstrates the charge-discharge performance of a 0.25M (mol / L) MgCl2-DME electrolyte with 30% trimethyl phosphate added in a Mg||Mg symmetrical cell, with a constant current charge-discharge density of 0.1 mA / cm². -2 Constant capacity 0.05mAh cm -2 Even when triethyl phosphate was replaced with trimethyl phosphate, the symmetrical cell still exhibited a low overpotential, indicating that the high dielectric constant of the organic phosphorus molecule improved the solubility of inorganic magnesium salts in DME while also enhancing the interfacial charge transfer kinetics. Examples 7-8 demonstrate the charge-discharge performance of electrolytes with different concentrations of triethyl phosphate added to 0.5 M (mol / L) MgCl2-DME electrolyte in a Mg||Mg symmetrical cell, with a constant current charge-discharge current density of 0.1 mA / cm². -2 Constant capacity 0.05mAh cm -2 Doubling the main salt concentration and adding different concentrations of triethyl phosphate, the symmetrical cell still exhibited a low overpotential and maintained cycling performance for over 800 hours. This indicates that this type of electrolyte possesses excellent electrochemical performance of the magnesium metal anode.

[0068] Figure 5The graphs show the rate polarization performance of the electrolytes prepared in Examples 1-5 and Examples 7-8 in a Mg||Mg symmetric cell at different current densities (where a is Example 1, b is Example 2, c is Example 3, d is Example 4, e is Example 5, f is Example 7, and g is Example 8), with a constant areal capacity of 0.2 mAh cm⁻¹. -2 The addition of triethyl phosphate significantly improved the limit of tolerable current density, even when the current density was increased from 0.05 mA / cm². -2 Increased to 6mAcm -2 It can also maintain stable magnesium metal dissolution / deposition behavior, indicating that this type of electrolyte has excellent rate performance.

[0069] Figure 6 The charge-discharge curves and cycle stability of the magnesium anodes prepared in Examples 9-10 and Comparative Example 3 in their respective electrolytes are shown (where a is Comparative Example 3, b is Example 9, and c is Example 10). The test results demonstrate the charge-discharge performance of electrolytes with different concentrations of triethyl phosphate added to a 0.25 M (mol / L) MgCl2-THF electrolyte in a Mg||Mg symmetric battery, with a constant current charge-discharge current density of 0.1 mA cm⁻¹. -2 Constant capacity 0.05mAh cm -2 Inorganic magnesium chloride salts can be completely dissolved in THF. Adding different proportions of triethyl phosphate can accelerate the dissolution rate and reduce the polarization potential. The preferred concentration of 20% triethyl phosphate has the lowest overpotential in its symmetrical cell and has been cycled for nearly 1000 hours. This indicates that even when THF is used as a solvent, the triethyl phosphate additive can significantly reduce the overpotential of magnesium metal dissolution / deposition and improve ionic conductivity.

[0070] Figure 7 The following are rate polarization performance curves of the electrolytes prepared in Examples 9-10 and Comparative Example 3 in a Mg||Mg symmetric battery at different current densities (where a is Comparative Example 3, b is Example 9, and c is Example 10), with a constant areal capacity of 0.2 mAh cm⁻¹. -2 When tetrahydrofuran is used as a solvent, the addition of different proportions of triethyl phosphate significantly improves the limit of tolerable current density, even when the current density increases from 0.05 mA cm⁻¹. -2 Increased to 6mA cm -2 It also maintains stable magnesium metal dissolution / deposition behavior, indicating that this type of electrolyte has excellent rate performance. However, compared to solvent DME, its rate performance is slightly worse.

[0071] Figure 8The images show the EIS diagrams of the electrolytes prepared in Examples 1-5 before and after cycling in a Mg||Mg symmetric cell (where a is Example 1, b is Example 2, c is Example 3, d is Example 4, and e is Example 5). The test results show that electrolytes with different concentrations of triethyl phosphate require cycling to achieve very low interfacial transfer resistance. They also demonstrate that the addition of triethyl phosphate significantly reduces the interfacial transfer resistance, indicating that its excellent charge transfer kinetics require a small-current electrochemical regulation process. This also shows that this type of electrolyte possesses excellent electrochemical performance as a magnesium metal anode.

[0072] Figure 9 The LSV diagrams for the electrolytes prepared in Examples 1-5 are shown in asymmetric cells (Mg||Al, Mg||Cu, Mg||SS, Mg||Ti, Mg||Mo cells) composed of different research electrodes and magnesium electrodes (where a is Example 1, b is Example 2, c is Example 3, d is Example 4, and e is Example 5). The test results are shown in the voltage range of OCV to 6.5V and the scan rate of 5mV s. -1 Under these conditions, the electrochemical window of the electrolyte in different working electrodes is greater than 2.5V, indicating that this type of electrolyte has a wide electrochemical window.

[0073] Figure 10 The figures show the charge-discharge curves and coulombic efficiency of the electrolyte prepared in Example 4 in asymmetric cells composed of different research electrodes (SS, Ti) and magnesium electrodes (Figures a and b correspond to the charge-discharge curves and coulombic efficiency of the SS working electrode, and Figures c and d correspond to the charge-discharge curves and coulombic efficiency of the Ti working electrode). The test results are shown at 0.05 mA cm⁻¹. -2 Under different current density conditions, reversible dissolution-deposition cycles can be performed on different working electrodes, with low deposition and dissolution overpotentials. The average coulombic efficiency can be maintained at over 90% for nearly 2100 cycles. These test results demonstrate that this type of electrolyte exhibits excellent magnesium metal dissolution / deposition performance.

[0074] Figure 11 The XRD patterns of the magnesium electrode after cycling in a Mg||Mg symmetric cell with the electrolytes prepared in Examples 1-5 are shown. The test results show that the magnesium metal anode deposit is mainly composed of elemental magnesium, and the characteristic peaks of the XRD images after battery cycling correspond to the magnesium metal PDF card, indicating that there is no significant change in the phase composition on the magnesium electrode surface.

[0075] Figure 12SEM images of the electrolytes prepared in Examples 1-5 after magnesium metal dissolution / deposition electrochemical testing (where a is Example 1, b is Example 2, c is Example 3, d is Example 4, and e is Example 5). The test results show that after charge-discharge, the magnesium electrode surface exhibits a uniform and dense magnesium deposit, indicating that this type of electrolyte has excellent magnesium metal anode electrochemical performance.

[0076] Figure 13 The Fourier transform infrared (FTIR) spectra of the electrolytes prepared in Examples 4, 10, and Comparative Example 2 are shown. The test results demonstrate the effects of adding different concentrations of triethyl phosphate at 1022 cm⁻¹. -1 The peak at 1260cm -1 The peak at 1106 cm⁻¹ matches the characteristic peaks of TEP, corresponding to the COP and P=O bonds of TEP, respectively. -1 The peak at 1067 cm⁻¹ corresponds to the COC bond in DME. -1 The spike at that point corresponds to the COC bond in THF.

Claims

1. An inorganic magnesium salt electrolyte for rechargeable magnesium batteries, characterized in that, The electrolyte salt is an inorganic magnesium salt, the inorganic magnesium salt is magnesium chloride; the electrolyte additive is an organic phosphorus molecule, and the volume fraction of the organic phosphorus molecule in the electrolyte is 5-40%.

2. The rechargeable magnesium battery inorganic magnesium salt electrolyte of claim 1, wherein, The volume fraction of the organic phosphorus molecule in the electrolyte is 20-40%.

3. The rechargeable magnesium battery inorganic magnesium salt electrolyte of claim 1, wherein, The organic ether solvent is one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane and 1,4-dioxane.

4. The rechargeable magnesium battery inorganic magnesium salt electrolyte of claim 1, wherein, The organic phosphorus molecule is at least one of trimethyl phosphate, triethyl phosphate, dibutyl phosphate and trimethyl phosphite.

5. The rechargeable magnesium battery inorganic magnesium salt electrolyte of claim 1, wherein, The molar concentration of the electrolyte salt in the electrolyte is 0.1-1.0 mol / L.

6. The rechargeable magnesium battery inorganic magnesium salt electrolyte of claim 5, wherein, The molar concentration of the electrolyte salt in the electrolyte is 0.25-0.5 mol / L.

7. A method for preparing the inorganic magnesium salt electrolyte of the rechargeable magnesium battery of claim 1, characterized by, The method comprises the following steps: (1) adding an inorganic magnesium salt into an organic ether solvent, stirring to dissolve and disperse the inorganic magnesium salt to obtain a reaction solution; (2) adding an electrolyte additive into the reaction solution, continuing to stir, and obtaining an inorganic magnesium salt electrolyte for rechargeable magnesium batteries after fully mixing.

8. The production method according to claim 7, characterized by, Steps (1) and (2) are performed in an argon glove box with water and oxygen contents both lower than 0.1 ppm; the stirring conditions are as follows: the stirring temperature is 40-90 ℃, the stirring speed is 300-1000 r / min, and the stirring time is 10-20 min.

9. Application of the inorganic magnesium salt electrolyte for rechargeable magnesium batteries in claim 1 in symmetric batteries and asymmetric batteries in magnesium ion batteries.

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