Rechargeable magnesium battery electrolyte and preparation method thereof

Abstract

The invention provides a rechargeable magnesium battery electrolyte and a preparation method thereof. The rechargeable magnesium battery electrolyte comprises magnesium trifluoromethanesulfonate, aluminum chloride, a sulfamide functional additive and an ether organic solvent, according to the prepared rechargeable magnesium battery electrolyte, reversible deposition-dissolution of magnesium can be achieved through the synergistic effect of all the components, the electrolyte is endowed with the characteristics of being good in affinity with a magnesium negative electrode, small in overpotential and high in magnesium deposition-dissolution efficiency, and good application prospects are achieved; moreover, the electrolyte is prepared in situ in one step by adopting a room-temperature stirring mode, the cost is low, and the preparation process has few steps, is simple to operate and is suitable for large-scale popularization and production.

Description

Technical Field

[0001] The invention relates to the technical field of secondary energy storage batteries, and in particular to a rechargeable magnesium battery electrolyte and a preparation method thereof. Background Art

[0002] The continuous use of fossil energy has led to serious environmental pollution problems. In the context of global environmental governance, it is crucial to develop green, clean, and efficient large-scale energy storage devices. Lithium-ion batteries have high specific energy and low self-discharge rate and are widely used in electronic devices and electric vehicles. However, limitations related to lithium resource allocation and rising raw material costs have seriously hindered the development of lithium-ion batteries. Therefore, it is necessary to explore alternative energy storage systems other than lithium-ion batteries. Monovalent sodium ions (Na + 、Divalent magnesium ion (Mg 2+ ), calcium ions (Ca 2+ ), zinc ion (Zn 2+ ) and trivalent aluminum ions (Al 3+ ) is used as a rechargeable ion battery. Among them, magnesium (Mg) metal exhibits low current potential, large volume capacity and high specific capacity. Moreover, the natural abundance of magnesium in the earth's crust is as high as 2.3%, which makes rechargeable magnesium batteries have advantages in production costs. In addition, the deposited magnesium is not easy to form dendrites on the negative electrode, which makes the battery safer. Therefore, rechargeable magnesium batteries are considered to be a strong competitor to replace lithium-ion batteries.

[0003] However, there is a significant performance gap between rechargeable magnesium batteries and lithium-ion batteries. The magnesium salt anions in the electrolyte decompose, resulting in the formation of a passivation layer containing MgO and MgS. The passivation layer seriously hinders the Mg 2+ The transport of ions leads to irreversible electrochemistry in magnesium batteries. In rechargeable magnesium batteries, the electrolyte is used to transport Mg between the cathode and the anode. 2+ Optimizing the electrolyte is the key method to solve the above problems.

[0004] Ether electrolytes based on Mg(CF3SO3)2 have the advantages of high voltage window, high reduction stability and simple preparation, and are considered to be one of the most promising electrolytes for rechargeable magnesium batteries. However, this type of electrolyte has extremely abnormal magnesium deposition / dissolution overpotential; moreover, it is very sensitive to impurities, and the performance of reagents produced by different suppliers also varies significantly. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a rechargeable magnesium battery electrolyte and a preparation method thereof. The rechargeable magnesium battery electrolyte prepared by the present invention can realize the reversible deposition-dissolution of magnesium through the synergistic effect between the components, and endows the electrolyte with the characteristics of good affinity with the magnesium negative electrode, small overpotential, and high magnesium deposition-dissolution efficiency, and has good application prospects; and the electrolyte of the present invention is prepared in situ in one step by stirring at room temperature, with low cost, few preparation process steps, simple operation, and suitable for large-scale promotion and production.

[0006] The technical solution of the present invention is as follows:

[0007] A rechargeable magnesium battery electrolyte comprises magnesium trifluoromethanesulfonate, aluminum chloride, a sulfonamide functional additive and an ether organic solvent.

[0008] Preferably, the sulfonamide functionalized additive is one or more of p-toluenesulfonamide, methanesulfonamide, ethanesulfonamide, benzenesulfonamide, sulfonamide, propylsulfonamide, ethylenesulfonamide, p-toluenesulfonamide, benzenesulfonamide, fluorosulfonamide, N-benzylsulfonamide, and p-toluenesulfonylacetamide.

[0009] More preferably, the sulfonamide functionalized additive is one or more of p-toluenesulfonamide, ethylenesulfonamide, and sulfonamide.

[0010] Further preferably, the sulfonamide functionalized additive is p-toluenesulfonamide.

[0011] The present invention preferably uses p-toluenesulfonamide as a sulfonamide functionalized additive, which not only has traditional ion coordination ability, but also can form a dynamic adaptive coordination structure with the solvent and magnesium ions, thereby improving the comprehensive performance of the magnesium battery electrolyte. On the surface of the magnesium anode, p-toluenesulfonamide (PTSA) can form a dense protective film, thereby enhancing the stability of the interface between the electrode and the electrolyte. This protective film covers the surface of the anode by adsorption and self-assembly, forming a physical barrier to prevent the active substances in the electrolyte from directly contacting the anode, which can effectively reduce the occurrence of adverse side reactions and help to extend the cycle life of the battery.

[0012] At the same time, p-toluenesulfonamide also has high electrochemical stability, can remain stable in a wide potential window, and is not prone to decomposition or side reactions. This feature ensures that it can play a role in the electrolyte for a long time, further improving the cycle performance of the battery.

[0013] Preferably, the concentration of the magnesium trifluoromethanesulfonate in the ether organic solvent is 0.01-2 mol / L; the molar ratio of the magnesium trifluoromethanesulfonate to the sulfonamide functional additive is 1:(0.5-1).

[0014] Further preferably, the molar ratio of the magnesium trifluoromethanesulfonate to the sulfonamide functional additive is 1:1.

[0015] Further preferably, the concentration of the magnesium trifluoromethanesulfonate in the ether organic solvent is 0.1-0.5 mol / L.

[0016] Preferably, the ether organic solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0017] Preferably, the molar ratio of magnesium trifluoromethanesulfonate to aluminum chloride is 1-5:1.

[0018] As a general inventive concept, the present invention provides a method for preparing a rechargeable magnesium battery electrolyte, comprising the following steps: mixing and stirring magnesium trifluoromethanesulfonate, aluminum chloride, a sulfonamide functional additive and an ether organic solvent to dissolve to obtain a rechargeable magnesium battery electrolyte.

[0019] The beneficial technical effects of the present invention are:

[0020] 1. The sulfonamide functionalized additive of the present invention is combined with magnesium trifluoromethanesulfonate to form an optimized electrolyte system. The oxygen atoms and sulfur atoms in the sulfonamide structure can interact closely with the polar solvent molecules in the electrolyte through hydrogen bonds and other weak interactions to form an adaptive solvent shell. This dynamically adjusted shell ensures the stable conduction of magnesium ions in different electrode states during the battery charge and discharge cycle, and effectively reduces the side reactions between the solvent and the negative electrode. In addition, the interaction between the sulfonamide group and magnesium trifluoromethanesulfonate further optimizes the chemical stability of the electrolyte and enhances the cycle performance and overall energy efficiency of the magnesium battery. Through this additive system, not only can the service life of the battery be extended, but the high rate performance of the battery is also significantly improved, successfully overcoming the bottleneck problem in the prior art. This synergistic effect fully reflects the potential of each component in improving battery performance.

[0021] 2. In the present invention, AlCl3, as an electrolyte additive, can effectively regulate the deposition behavior of magnesium ions and the electrochemical properties of the electrolyte. Specifically, AlCl3 can change the solvation environment of magnesium ions, enhance the transmission capacity of magnesium ions, and reduce the occurrence of side reactions on the surface of the magnesium electrode by forming complex ions (such as [MgAlCl4]+) with magnesium ions in the electrolyte. This mechanism helps to improve the reversibility and charge and discharge efficiency of magnesium batteries. By adding AlCl3, the conductivity, stability and electrochemical window of the electrolyte are optimized, thereby improving the reversible deposition and dissolution behavior of magnesium ions. The introduction of AlCl3 not only helps to reduce the formation of a passivation layer on the magnesium surface, but also can effectively reduce the risk of dendrite formation and improve the cycle stability of the battery.

[0022] 3. The electrolyte of the present invention preferably uses an organic solvent of ethylene glycol dimethyl ether as a solvent, which forms a stable solvation shell with the magnesium ions in the electrolyte to ensure that the magnesium ions can be efficiently conducted during the charge and discharge process. Specifically, the organic solvent molecules of ethylene glycol dimethyl ether establish a balanced solvation environment with the magnesium ions through weak intermolecular interactions, reducing the occurrence of dendrite formation and side reactions, thereby achieving a more stable magnesium deposition and dissolution process. In addition, the dynamic interaction between the solvent molecules and the polar groups in the electrolyte can adaptively adjust the structure of the solvent shell according to the different charge and discharge states of the battery, ensuring the smooth transmission of magnesium ions between the negative electrode and the positive electrode. This adaptive shell adjustment not only effectively enhances the reversible deposition of magnesium ions, but also improves the interface stability between the electrolyte and the magnesium negative electrode.

[0023] Through the optimized design of the solvent, the present invention successfully overcomes the limitations of the traditional tetrahydrofuran solvent system in magnesium batteries, significantly improves the cycle stability and charge and discharge efficiency of magnesium batteries, and prolongs the service life of the battery. The synergistic effect of this solvent and magnesium electrolyte fully demonstrates the huge potential for improving electrochemical performance in magnesium battery technology.

[0024] 4. The rechargeable magnesium battery electrolyte based on sulfonamide functionalized additives of the present invention is simple and feasible, low in cost, has few preparation process steps, is easy to operate, and is suitable for large-scale promotion and production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a long cycle performance diagram of the Mg / / Mg symmetric battery prepared with the electrolyte in Example 1;

[0026] Figure 2 is a long cycle performance diagram of the Mg / / Mg symmetric battery prepared with the electrolyte in Example 2;

[0027] Figure 3 is a long cycle performance diagram of a Mg / / Mg symmetric battery prepared with the electrolyte in Example 8;

[0028] Figure 4 This is a long cycle performance diagram of the Mg / / Mg symmetric battery prepared using the electrolyte in Comparative Example 1. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1:

[0031] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1 ppm, 0.645 g of magnesium trifluoromethanesulfonate and 0.133 g of aluminum chloride were weighed and placed in a reagent bottle, 10 ml of diethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.342 g of p-toluenesulfonamide was added, and magnetic stirring was continued for 12 h to obtain a rechargeable magnesium battery electrolyte.

[0032] Embodiment 2:

[0033] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1 ppm, 0.645 g of magnesium trifluoromethanesulfonate and 0.133 g of aluminum chloride were weighed and placed in a reagent bottle, 10 ml of ethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.342 g of p-toluenesulfonamide was added, and magnetic stirring was continued for 12 h to obtain a rechargeable magnesium battery electrolyte.

[0034] Embodiment 3:

[0035] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1ppm, 0.322g of magnesium trifluoromethanesulfonate and 0.133g of aluminum chloride were weighed and placed in a reagent bottle, 10ml of diethylene glycol dimethyl ether was transferred into the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.172g of sulfonamide was added, and magnetic stirring was continued for 12h to obtain a rechargeable magnesium battery electrolyte.

[0036] Embodiment 4:

[0037] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1ppm, 1.612g of magnesium trifluoromethanesulfonate and 0.133g of aluminum chloride were weighed and placed in a reagent bottle, 10ml of tetraethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.856g of p-toluenesulfonamide was added, and magnetic stirring was continued for 12h to obtain a rechargeable magnesium battery electrolyte.

[0038] Embodiment 5:

[0039] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1ppm, 0.322g of magnesium trifluoromethanesulfonate and 0.133g of aluminum chloride were weighed and placed in a reagent bottle, 10ml of diethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.109g of ethanesulfonamide was added, and magnetic stirring was continued for 12h to obtain a rechargeable magnesium battery electrolyte.

[0040] Embodiment 6:

[0041] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1 ppm, 1.612 g of magnesium trifluoromethanesulfonate and 0.133 g of aluminum chloride were weighed and placed in a reagent bottle, 10 ml of ethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.861 g of sulfonamide was added, and magnetic stirring was continued for 12 h to obtain a rechargeable magnesium battery electrolyte.

[0042] Embodiment 7:

[0043] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1 ppm, 1.612 g of magnesium trifluoromethanesulfonate and 0.133 g of aluminum chloride were weighed and placed in a reagent bottle, 10 ml of tetraethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.431 g of sulfonamide was added, and magnetic stirring was continued for 12 h to obtain a rechargeable magnesium battery electrolyte.

[0044] Embodiment 8:

[0045] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1 ppm, 0.645 g of magnesium trifluoromethanesulfonate and 0.133 g of aluminum chloride were weighed and placed in a reagent bottle, 10 ml of diethylene glycol dimethyl ether was transferred to the reagent bottle using a pipette, and magnetic stirring was performed. After the magnesium trifluoromethanesulfonate was completely dissolved, 0.109 g of ethanesulfonamide was added, and magnetic stirring was continued for 12 h to obtain a rechargeable magnesium battery electrolyte.

[0046] Comparative Example 1:

[0047] In a circulating purification glove box with water and oxygen contents below 0.1ppm, weigh 0.322g of magnesium trifluoromethanesulfonate and 0.133g of aluminum chloride and place them in a reagent bottle, use a pipette to transfer 10ml of ethylene glycol dimethyl ether into the reagent bottle, stir magnetically, and after the magnesium trifluoromethanesulfonate is completely dissolved, add 0.170g of methyl p-toluenesulfone, continue magnetic stirring for 12h to obtain an electrolyte.

[0048] Comparative Example 2:

[0049] In a circulating purification glove box with water and oxygen contents below 0.1ppm, weigh 1.612g of magnesium trifluoromethanesulfonate and 0.133g of aluminum chloride and place them in a reagent bottle, use a pipette to transfer 10ml of diethylene glycol dimethyl ether into the reagent bottle, stir magnetically, and after the magnesium trifluoromethanesulfonate is completely dissolved, add 0.026g of lithium fluoride, continue magnetic stirring for 12h to obtain an electrolyte.

[0050] Comparative Example 3:

[0051] In a circulating purification glove box with a water content and an oxygen content both lower than 0.1 ppm, weigh 0.645 g of magnesium trifluoromethanesulfonate, use a pipette to transfer 10 ml of diethylene glycol dimethyl ether into a reagent bottle, stir magnetically, and after the magnesium trifluoromethanesulfonate is completely dissolved, add 0.342 g of p-toluenesulfonamide, continue magnetic stirring for 12 h, and obtain an electrolyte.

[0052] Comparative Example 4:

[0053] In a circulating purification glove box with water and oxygen contents below 0.1ppm, weigh 1.612g of magnesium trifluoromethanesulfonate and 0.133g of aluminum chloride and place them in a reagent bottle, use a pipette to transfer 10ml of tetrahydrofuran into the reagent bottle, stir magnetically, and after the magnesium trifluoromethanesulfonate is completely dissolved, add 0.273g of ethanesulfonamide, continue magnetic stirring for 12h to obtain an electrolyte.

[0054] test:

[0055] (1) Ionic conductivity test

[0056] The electrolytes in Examples 1-8 and Comparative Examples 1-4 were used as electrolytes, a certain amount of electrolyte was dripped onto the glass fiber, stainless steel sheets were used as blocking electrodes on both sides, and CR2032 batteries were assembled. AC impedance tests were performed using a Chenhua 650E electrochemical workstation. The voltage amplitude during the test was 5mV, and the test frequency range was 10 5 Hz-0.01Hz, the test temperature is room temperature. The resistance Rs (Ω) of the electrolyte is obtained by the AC impedance spectrum, and then the ionic conductivity of the electrolyte is obtained by the following conductivity definition formula:

[0057] The calculation formula of ionic conductivity is:

[0058]

[0059] Where σ—ionic conductivity, S·cm -1 ;

[0060] L—electrolyte thickness, cm;

[0061] R—Electrolyte resistance obtained by test, Ω;

[0062] S—cross-sectional area of ​​glass fiber diaphragm, cm 2 .

[0063] (2) Overpotential test

[0064] The electrolytes in Examples 1-8 and Comparative Examples 1-4 were used as electrolytes, a certain amount of electrolyte was dripped onto the glass fiber, a Mg / / Mg symmetrical battery was assembled, and a constant current charge and discharge test was performed using a blue power test system.

[0065] The test results of ionic conductivity and overpotential are shown in Table 1.

[0066] Table 1 Ionic conductivity and overpotential test results

[0067] <![CDATA[Ionic conductivity / mS·cm -1 > Overpotential / mV Example 1 3.58 340 Example 2 3.45 350 Example 3 2.13 450 Example 4 3.22 380 Example 5 1.72 500 Example 6 1.29 550 Example 7 2.02 450 Example 8 1.43 530 Comparative Example 1 0.76 1000 Comparative Example 2 0.53 1500 Comparative Example 3 1.29 3000 Comparative Example 4 / /

[0068] As can be seen from Table 1, by comparing the examples and comparative examples 1-2, it can be seen that compared with the electrolyte without sulfonamide functionalized additives, the electrolyte containing sulfonamide functionalized additives exhibits high ionic conductivity and low overpotential. And by comparing Example 1 with other examples, it can be seen that when the concentration of magnesium trifluoromethanesulfonate in the ether organic solvent is 0.2 mol / L, and the molar ratio of magnesium trifluoromethanesulfonate to the sulfonamide functionalized additive is 1:1, the electrolyte exhibits higher ionic conductivity and low overpotential. As can be seen from Comparative Example 3, when aluminum chloride is not contained in the electrolyte, the overpotential will increase significantly. As can be seen from Comparative Example 4, when the solvent of the electrolyte is tetrahydrofuran, reversible deposition and dissolution of magnesium ions cannot be achieved.

[0069] In addition, the electrolytes in Examples 1, 2, 8 and Comparative Example 1 were used as electrolytes to assemble CR2032 type Mg / / Mg symmetrical batteries. Constant current charge and discharge tests were performed using the LAND battery test system, with a test current density of 0.5 mA / cm 2 The test procedure is to discharge for 30 minutes and charge for 30 minutes, and repeat the charge and discharge to test the electrolyte polarization performance. The test results show that the electrolytes of Examples 1, 2, and 8 can work stably at low deposition potential for 1070 hours, 630 hours, and 620 hours, respectively (such as Figure 1-3 The electrolyte of Comparative Example 1 can only circulate for 220h (as shown); Figure 4 shown).

[0070] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes, and can be fully applicable to various fields suitable for the present invention. For those familiar with the art, for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A rechargeable magnesium battery electrolyte, characterized in that: The invention comprises magnesium trifluoromethanesulfonate, aluminum chloride, sulfonamide functional additives and ether organic solvents.

2. The rechargeable magnesium battery electrolyte according to claim 1, characterized in that: The sulfonamide functionalized additive is one or more of p-toluenesulfonamide, methanesulfonamide, ethanesulfonamide, benzenesulfonamide, sulfonamide, propylsulfonamide, ethylenesulfonamide, p-toluenesulfonamide, benzenesulfonamide, fluorosulfonamide, N-benzylsulfonamide, and p-toluenesulfonylacetamide.

3. The rechargeable magnesium battery electrolyte according to claim 2, characterized in that: The sulfonamide functionalized additive is one or more of p-toluenesulfonamide, ethylenesulfonamide and sulfonamide.

4. The rechargeable magnesium battery electrolyte according to claim 3, characterized in that: The sulfonamide functionalized additive is p-toluenesulfonamide.

5. The rechargeable magnesium battery electrolyte according to claim 1, characterized in that: The concentration of the magnesium trifluoromethanesulfonate in the ether organic solvent is 0.01-2 mol / L; the molar ratio of the magnesium trifluoromethanesulfonate to the sulfonamide functional additive is 1:(0.5-1).

6. The rechargeable magnesium battery electrolyte according to claim 5, characterized in that: The molar ratio of the magnesium trifluoromethanesulfonate to the sulfonamide functional additive is 1:

1.

7. The rechargeable magnesium battery electrolyte according to claim 5, characterized in that: The concentration of the magnesium trifluoromethanesulfonate in the ether organic solvent is 0.1-0.5 mol / L.

8. The rechargeable magnesium battery electrolyte according to claim 1, characterized in that: The ether organic solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

9. The rechargeable magnesium battery electrolyte according to claim 1, characterized in that: The molar ratio of the magnesium trifluoromethanesulfonate to the aluminum chloride is 1-5:

1.

10. A method for preparing a rechargeable magnesium battery electrolyte as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Magnesium trifluoromethanesulfonate, aluminum chloride, sulfonamide functional additive and ether organic solvent are mixed, stirred and dissolved to obtain a rechargeable magnesium battery electrolyte.

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