Electrolyte for magnesium secondary battery, preparation method of electrolyte and magnesium secondary battery
By introducing a ternary co-solvent system of traditional magnesium salt, ether solvent, amine solvent and phosphate ester solvent into the electrolyte for magnesium secondary batteries, the problem of poor compatibility between the electrolyte for magnesium secondary batteries and the metallic magnesium anode is solved, achieving the effects of high ionic conductivity, low magnesium electrodeposition overpotential and long cycle life.
Patent Information
- Application Number
- CN202511864468.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-03-03
AI Technical Summary
Traditional magnesium secondary batteries have poor compatibility between the electrolyte and the magnesium anode, resulting in problems such as abnormally high magnesium deposition/dissolution overpotential, sensitivity to trace amounts of water and oxygen impurities, poor stability of the interface passivation layer, and short cycle life.
A ternary co-solvent system consisting of traditional magnesium salt, ether solvent, amine solvent, and phosphate ester solvent is adopted. Active ion pairs are formed through group exchange reactions between ether, amine, and phosphate ester, thereby improving the compatibility between the electrolyte and the magnesium anode.
It achieves high ionic conductivity, low magnesium electrodeposition overpotential and long cycle life, and the electrolyte formulation is simple, non-corrosive and low in cost.
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Figure CN121601792A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of secondary energy storage battery technology, specifically relating to an electrolyte for magnesium secondary batteries based on a ternary co-solvent system of ether, amine and phosphate ester, its preparation method, and a magnesium secondary battery. Background Technology
[0002] In recent years, magnesium secondary batteries have been regarded as an important candidate for next-generation high-safety energy storage devices due to their high volumetric energy density (3833 mAh / cm³), dendrite-free characteristics, and abundant magnesium resources. However, their development is limited by the compatibility between magnesium metal anodes and magnesium ion electrolytes. There are three main types of electrolytes used in traditional magnesium secondary batteries: first, magnesium ion electrolytes containing halogenated Grignard reagent derivatives, such as all-phenyl complex electrolytes; second, magnesium ion electrolytes with boron or aluminum as anionic centers, such as organoboronate magnesium ion electrolytes composed of magnesium tetra(hexafluoroisopropoxy)borate and ether solvents; and third, traditional magnesium salt electrolytes based on traditional magnesium salts and ether solvents, such as magnesium ion electrolytes composed of magnesium bis(trifluoromethanesulfonyl)imide and ethylene glycol dimethyl ether.
[0003] The above-mentioned magnesium ion electrolytes have many problems. For example, the all-phenyl complex electrolyte is corrosive due to the presence of halide ions, the synthesis of organoboroester magnesium ion electrolytes is complex and costly, and traditional magnesium salt electrolytes exhibit incompatibility with metallic magnesium anodes, mainly manifested in (1) an abnormally high magnesium deposition / dissolution overpotential (approximately -2.0V vs. Mg). 2+ / Mg); (2) High sensitivity to trace amounts of water and oxygen impurities; (3) Poor stability of the interface passivation layer leading to short cycle life (usually <200 hours).
[0004] Literature studies have shown that the compatibility between traditional magnesium salt electrolytes and metallic magnesium anodes can be improved by adding amine solvents or phosphate co-solvents. However, ether-amine binary solvents still suffer from problems such as hydrogen evolution reaction and magnesium anode corrosion, while ether-phosphate co-solvents react with the magnesium anode interface to generate interfacial products such as magnesium phosphate. These problems severely affect the compatibility between magnesium ion electrolytes and positive and negative electrode materials, resulting in short cycle life and low specific capacity in magnesium secondary batteries. Summary of the Invention
[0005] To address the problem of poor compatibility between traditional magnesium salt electrolytes and metallic magnesium anodes, the primary objective of this invention is to provide an electrolyte for magnesium secondary batteries and its preparation method.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: An electrolyte for magnesium secondary batteries is disclosed, comprising a conventional magnesium salt, an ether solvent, an amine solvent, and a phosphate ester solvent. The concentration of the conventional magnesium salt is 0.02-4 mol / L; the volume percentage of the ether solvent in the electrolyte is 20%-90%; the volume percentage of the amine solvent is 5%-40%; and the volume percentage of the phosphate ester solvent is 5%-40%.
[0007] Furthermore, the conventional magnesium salt is magnesium bis(trifluoromethanesulfonyl)imide or magnesium trifluoromethanesulfonate, preferably magnesium trifluoromethanesulfonate.
[0008] Furthermore, the concentration of the conventional magnesium salt in the electrolyte for magnesium secondary batteries is preferably 0.1-2 mol / L; the volume percentage of the ether solvent in the electrolyte for magnesium secondary batteries is preferably 50%-90%; the volume percentage of the amine solvent in the electrolyte for magnesium secondary batteries is preferably 5%-25%; and the volume percentage of the phosphate ester in the electrolyte for magnesium secondary batteries is preferably 5%-25%.
[0009] Further, the ether solvent is one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; the amine solvent is one or more of 2-methoxyethylamine, 1-methoxy-2-propylamine, 3-methoxypropylamine, 3-dimethylaminopropylamine, and furfurylamine; and the phosphate ester solvent is one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, and dibutyl phosphate.
[0010] Further, the ether solvent is preferably diethylene glycol dimethyl ether; the amine solvent is preferably 3-methoxypropylamine and 3-dimethylaminopropylamine; and the phosphate ester solvent is preferably trimethyl phosphate.
[0011] The method for preparing the electrolyte for magnesium secondary batteries includes the following steps: under an inert atmosphere, an ether solvent and an amine solvent are mixed to form a binary mixed solvent, a conventional magnesium salt is added, and the mixture is stirred continuously until completely dissolved. Finally, a phosphate ester solvent is added, and an electrochemically active species structure is formed through an inter-amine-phosphate ester group exchange reaction. The electrolyte is obtained after stirring continuously until completely dissolved.
[0012] Furthermore, the inert atmosphere has H2O < 10 ppm and O2 < 1 ppm, and the ether solvent and amine solvent are mixed and stirred for 1-2 hours.
[0013] Another object of the present invention is to provide a magnesium secondary battery, wherein the electrolyte is the above-mentioned electrolyte for magnesium secondary batteries, the negative electrode is a magnesium foil, and the positive electrode is one or a composite of Mo6S8, MnO2, CuS, Cu3Se2 and polyaniline.
[0014] Furthermore, the electrolyte for the magnesium secondary battery is composed of a conventional magnesium salt, an ether solvent, an amine solvent, and a phosphate ester solvent. The ether solvent is diethylene glycol dimethyl ether, the amine solvent is 3-methoxypropylamine and 3-dimethylaminopropylamine, the phosphate ester solvent is trimethyl phosphate, and the magnesium salt is magnesium trifluoromethanesulfonate.
[0015] By adopting the above technical solution, the present invention achieves the following technical effects: The electrolyte for magnesium secondary batteries of this invention comprises traditional magnesium salts, ether solvents, amine solvents, and phosphate ester solvents, etc., and improves the compatibility between the electrolyte and the metallic magnesium anode through the synergistic effect of the ternary solvents. The magnesium secondary battery electrolyte of this application has advantages such as high ionic conductivity (>9 mS / cm), low magnesium electrodeposition overpotential (<0.5V), and long cycle life of magnesium secondary batteries (>1000 cycles). Moreover, the electrolyte formulation is simple and halogen-free, and has the advantages of low cost and non-corrosiveness. Attached Figure Description
[0016] Figure 1 The constant current charge-discharge curve of the magnesium secondary battery electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 3-methoxypropylamine + trimethyl phosphate) provided in Example 1 of the present invention is shown. Figure 2 The cyclic voltammetry curves of the magnesium secondary battery electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 3-methoxypropylamine + trimethyl phosphate) provided in Example 1 of this invention are shown. Figure 3 The constant current charge-discharge curve of the magnesium secondary battery electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 3-methoxypropylamine + tributyl phosphate) provided in Example 2 of the present invention is shown. Figure 4 The constant current charge-discharge curve of the magnesium secondary battery electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 2-methoxyethylamine + dibutyl phosphate) provided in Example 3 of the present invention is shown. Figure 5 The constant current charge-discharge curve of the magnesium secondary battery electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 3-methoxypropylamine + dibutyl phosphate) provided in Example 4 of the present invention is shown. Figure 6 This is the constant current charge-discharge curve of the magnesium secondary battery electrolyte (1 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 3-dimethylaminopropylamine + triethyl phosphate)) provided in Example 5 of the present invention. Figure 7The constant current charge-discharge curves of the magnesium ion electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + trimethyl phosphate)) in Comparative Example 1 are shown. Figure 8 The constant current charge-discharge curves of the magnesium ion electrolyte (0.5 mol / L magnesium trifluoromethanesulfonate / (diethylene glycol dimethyl ether + 3-methoxypropylamine)) in Comparative Example 2 are shown. Detailed Implementation
[0017] The following embodiments are further illustrations of the present invention, but the present invention is not limited to the following embodiments.
[0018] Example 1 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of diethylene glycol dimethyl ether solvent into a glass bottle. Then, pipette 0.3 mL of 3-methoxypropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Pipette 0.2 mL of trimethyl phosphate and slowly add it dropwise until all the solution is added. Stir magnetically for 12 hours to finally obtain a colorless and transparent electrolyte.
[0019] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using the LAND battery testing system (see [link to test results]). Figure 1 The tested current density was 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the electrolyte could cycle stably for 1000 hours, demonstrating a significant performance improvement. Cyclic voltammetry tests were conducted using an electrochemical workstation (see [link to electrochemical workstation]). Figure 2 Further investigation was conducted on the magnesium deposition / dissolution properties at a scan rate of 25 mV / s. Experimental results showed that both reduction and oxidation peaks were present in the cyclic voltammetry curve of the electrolyte, indicating its ability to deposit / dissolve magnesium, consistent with the results of the constant current charge-discharge test. The test results also demonstrated that the electrolyte exhibited excellent overall performance, possessing a 9.847 mS... cm -1 It features high ionic conductivity and a low magnesium electrodeposition overpotential of 67mV, while also giving magnesium secondary batteries a long cycle life of over 1500 cycles. It also demonstrates outstanding performance in ion transport efficiency, deposition kinetics, and cycle stability.
[0020] Example 2 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of diethylene glycol dimethyl ether solvent into a glass bottle. Then, pipette 0.3 mL of 3-methoxypropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Finally, pipette 0.2 mL of tributyl phosphate and slowly add it dropwise until the solution is completely added. Stir magnetically for 12 hours to obtain a colorless and transparent electrolyte.
[0021] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using the LAND battery testing system (see [link to test results]). Figure 3 The tested current density was 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the electrolyte could cycle stably for over 2500 hours, exhibiting excellent interfacial compatibility with the magnesium anode and significantly improved performance. Test results also demonstrated that the electrolyte possessed excellent overall performance, exhibiting a conductivity of 9.686 mS. cm -1 Its high ionic conductivity and low magnesium electrodeposition overpotential of 60mV enable magnesium secondary batteries to achieve a long cycle life of over 1250 cycles, and it exhibits excellent performance in terms of ion migration efficiency, deposition reaction kinetics and cycle stability.
[0022] Example 3 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of diethylene glycol dimethyl ether solvent into a glass vial. Then, pipette 0.3 mL of 3-dimethylaminopropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Finally, pipette 0.2 mL of trimethyl phosphate and slowly add it dropwise. After the addition is complete, stir magnetically for 12 hours to obtain a colorless and transparent electrolyte.
[0023] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using the LAND battery testing system (see [link to test results]). Figure 4 The tested current density was 0.1 mAh / cm³. 2The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the electrolyte possessed a low magnesium deposition / dissolution overpotential, with the voltage remaining stable within a narrow range of -0.5V to 1.5V, and could operate stably for nearly 900 hours. The test results also demonstrated that the electrolyte exhibited excellent overall performance, with a voltage drop of 9.674 mS. cm -1 Its high ionic conductivity and low magnesium electrodeposition overpotential of 60mV enable magnesium secondary batteries to achieve a long cycle life of over 1200 cycles, demonstrating excellent performance in ion transport capability, deposition kinetics, and cycle stability.
[0024] Example 4 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of diethylene glycol dimethyl ether solvent into a glass bottle. Then, pipette 0.3 mL of 3-methoxypropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Finally, pipette 0.2 mL of dibutyl phosphate and slowly add it dropwise until the solution is completely added. Stir magnetically for 12 hours to obtain a colorless and transparent electrolyte.
[0025] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were conducted using the LAND battery testing system, and the measured current density was 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Cyclic voltammetry was performed using an electrochemical workstation (see [link to electrochemical workstation]). Figure 5 Further investigation was conducted on the magnesium deposition / dissolution performance at a scan rate of 25 mV / s. Experimental results showed that the electrolyte possessed a low magnesium deposition / dissolution overpotential, with the voltage stabilizing within a narrow range of -0.5 V to 1.5 V, and could operate stably for 2500 hours, far exceeding expectations. Test results also indicated that the electrolyte exhibited excellent overall performance, with a potential of 9.593 mS. cm -1 Its high ionic conductivity and low magnesium electrodeposition overpotential of 60mV enable magnesium secondary batteries to achieve a long cycle life of over 1200 cycles.
[0026] Example 5 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1 mL of diethylene glycol dimethyl ether solvent into a glass bottle. Then, pipette 0.5 mL of 3-dimethylaminopropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 0.644 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Finally, pipette 0.5 mL of triethyl phosphate and slowly add it dropwise until the solution is completely added. Stir magnetically for 12 hours to obtain a colorless and transparent electrolyte.
[0027] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, copper foil as the positive electrode, and a magnesium secondary battery with magnesium foil as the electrolyte. Constant current charge-discharge tests were performed using the LAND battery testing system (see [link to test details]). Figure 6 The tested current density was 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the electrolyte possessed a low magnesium deposition / dissolution overpotential, with the voltage fluctuating stably within a narrow range of -0.5V to 1.5V, and could operate stably for 1400 hours. It exhibited a voltage of 9.579 ms. cm -1 Its high ionic conductivity and low magnesium electrodeposition overpotential of 60mV enable magnesium secondary batteries to achieve a long cycle life of 695 cycles.
[0028] Example 6 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.6 mL of diethylene glycol dimethyl ether solvent into a glass bottle. Then, pipette 0.2 mL of 3-methoxypropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 1.754 g of magnesium bis(trifluoromethanesulfonyl)imide (purity ≥ 99.9%) and slowly add it to the above solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Pipette 0.2 mL of trimethyl phosphate and slowly add it dropwise until all the solution is added. Stir magnetically for 12 hours to finally obtain a colorless and transparent electrolyte.
[0029] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were conducted using a LAND battery testing system, with a test current density of 0.1 mAh / cm³. 2The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the electrolyte could cycle stably for 1000 hours, demonstrating a significant performance improvement. Cyclic voltammetry tests were conducted using an electrochemical workstation to further investigate magnesium deposition / dissolution performance at a scan rate of 25 mV / s. The results showed the presence of reduction and oxidation peaks in the cyclic voltammetry curves of the electrolyte, indicating its ability to deposit / dissolve magnesium, consistent with the results of the constant current charge-discharge test. The test results demonstrate that the electrolyte exhibits excellent comprehensive performance, possessing a 9.847 mS... cm -1 It features high ionic conductivity and a low magnesium electrodeposition overpotential of 65mV, while also giving magnesium secondary batteries a long cycle life of over 1500 cycles. It also demonstrates outstanding performance in ion transport efficiency, deposition kinetics, and cycle stability.
[0030] Example 7 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of tetrahydrofuran solvent into a glass bottle. Then, pipette 0.3 mL of 3-methoxypropylamine and add it to the above ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a colorless and transparent solution. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the above solution in three portions using a spatula, stirring magnetically until the solution turns a uniform pale yellow. Pipette 0.2 mL of trimethyl phosphate and slowly add it dropwise until all the solution is added. Stir magnetically for 12 hours to finally obtain a colorless and transparent electrolyte.
[0031] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were conducted using a LAND battery testing system, with a test current density of 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the electrolyte could cycle stably for 1000 hours, demonstrating a significant performance improvement. Cyclic voltammetry tests were conducted using an electrochemical workstation to further investigate magnesium deposition / dissolution performance at a scan rate of 25 mV / s. The results showed the presence of reduction and oxidation peaks in the cyclic voltammetry curves of the electrolyte, indicating its ability to deposit / dissolve magnesium, consistent with the results of the constant current charge-discharge test. The test results demonstrate that the electrolyte exhibits excellent comprehensive performance, possessing a 9.645 mS... cm -1 It features high ionic conductivity and a low magnesium electrodeposition overpotential of 60mV, while also giving magnesium secondary batteries a long cycle life of over 1800 cycles. It also demonstrates outstanding performance in ion transport efficiency, deposition kinetics, and cycle stability.
[0032] Comparative Example 1 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of diethylene glycol dimethyl ether solvent into a glass vial. Then, pipette 0.3 mL of trimethyl phosphate into the ether solution and magnetically stir (400 rpm, room temperature) for 1 hour to obtain a mixed solvent system. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically for 12 hours until the solution is fully mixed.
[0033] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using the LAND battery testing system (see [link to test results]). Figure 7 The tested current density was 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. Experimental results showed that the cycle life of this electrolyte system was only 300 hours, which did not meet the requirements.
[0034] Comparative Example 2 In an argon glove box (H2O < 1 ppm, O2 < 1 ppm), accurately pipette 1.5 mL of diethylene glycol dimethyl ether solvent into a glass vial. Then, pipette 0.3 mL of 3-methoxypropylamine and add it to the ether solution. Stir magnetically (400 rpm, room temperature) for 1 hour to obtain a mixed solvent system. Weigh 0.322 g of magnesium trifluoromethanesulfonate (purity ≥ 99.9%) and slowly add it to the solution in three portions using a spatula, stirring magnetically for 12 hours until the solution is fully mixed.
[0035] A CR2032 coin cell was assembled using magnesium foil as the negative electrode, the electrolyte from the aforementioned magnesium secondary battery, and copper foil as the positive electrode. Constant current charge-discharge tests were performed using the LAND battery testing system (see [link to test results]). Figure 8 The tested current density was 0.1 mAh / cm³. 2 The test procedure involved discharging for 1 hour, charging to 1.5V, and repeating the charge-discharge cycle. The test results showed that the electrolyte's cycle life was only 50 hours, far below the expected value, and thus failed to meet usage requirements.
[0036] In this invention, magnesium trifluoromethanesulfonate is dissolved in ether solvent, amine solvent, and phosphate ester solvent. The electrochemical performance is enhanced through the synergistic effect of the ether-amine-phosphate ternary solvent: the ether solvent acts as the main solvent for dissolving magnesium salts; the group exchange reaction between amine and phosphate ester forms an active ion pair structure and promotes the reversibility of the magnesium electrodeposition reaction. Taking the proton and alkyl exchange reaction mechanism between 3-methoxypropylamine and trimethyl phosphate as an example, the formation of the active species Mg[(CH3O)2PO2]2 in the electrolyte plays an important role in improving ionic conductivity, reducing the overpotential of magnesium electrodeposition, and extending the cycle life of the magnesium secondary battery. For co-solvents without group exchange reaction between amine and phosphate ester, such as tertiary amines (without active protons), it is difficult for them to undergo group exchange reaction with phosphate esters and form electrochemically active species structures. Therefore, the compatibility between the magnesium ion electrolyte and the magnesium anode is difficult to effectively solve.
Claims
1. An electrolyte for magnesium secondary batteries, characterized in that: It includes conventional magnesium salts, ether solvents, amine solvents, and phosphate ester solvents; wherein the concentration of conventional magnesium salts is 0.02-4 mol / L, the volume percentage of ether solvents is 20%-90%, the volume percentage of amine solvents is 5%-40%, and the volume percentage of phosphate esters is 5%-40%, and the conventional magnesium salts are bis(trifluoromethanesulfonyl)imide magnesium or trifluoromethanesulfonate magnesium.
2. The electrolyte for a magnesium secondary battery according to claim 1, characterized in that: The concentration of the conventional magnesium salt is 0.1-2 mol / L, the volume percentage of the ether solvent is 50%-80%, the volume percentage of the amine solvent is 10%-25%, and the volume percentage of the phosphate ester is 10%-25%.
3. The electrolyte for a magnesium secondary battery according to any one of claims 1 or 2, characterized in that: The ether solvent is selected from one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; the amine solvent is selected from one or more of 2-methoxyethylamine, 1-methoxy-2-propylamine, 3-methoxypropylamine, 3-dimethylaminopropylamine, and furfurylamine; the phosphate ester solvent is selected from one or more of trimethyl phosphate, triethyl phosphate, tributyl phosphate, and dibutyl phosphate.
4. The electrolyte for a magnesium secondary battery according to claim 3, characterized in that: The ether solvent is diethylene glycol dimethyl ether, the amine solvent is 3-methoxypropylamine, the phosphate ester solvent is trimethyl phosphate, and the conventional magnesium salt is magnesium trifluoromethanesulfonate.
5. A method for preparing an electrolyte for a magnesium secondary battery according to claim 1 or 2, characterized in that: Under an inert atmosphere, ether solvent and amine solvent are mixed and stirred to form a binary mixed solvent. A conventional magnesium salt is added and stirred until completely dissolved. A phosphate ester solvent is added and stirred until completely dissolved to obtain the electrolyte.
6. The method for preparing an electrolyte for a magnesium secondary battery according to claim 5, characterized in that: The inert atmosphere has H2O < 10 ppm and O2 < 1 ppm. The ether solvent and amine solvent are mixed and stirred for 1-2 hours.
7. A magnesium secondary battery, characterized in that: The electrolyte is the magnesium secondary battery electrolyte according to any one of claims 1-4, the negative electrode is a magnesium foil, and the positive electrode is one or more of Mo6S8, MnO2, CuS, Cu3Se2 and polyaniline.
8. A magnesium secondary battery according to claim 7, characterized in that: The magnesium secondary battery is a button cell or a pouch cell.