A composite rechargeable magnesium battery electrolyte and preparation method thereof

Abstract

The present invention provides a composite rechargeable magnesium battery electrolyte and a preparation method thereof. The electrolyte of the present invention contains an organic solvent, an electrolyte salt and an additive; during the preparation process, the raw materials are not subjected to any water removal and impurity removal pretreatment, and the electrolyte is obtained by directly stirring and mixing under an inert atmosphere at room temperature. The composite electrolyte of the present invention has high conductivity, low overpotential, high magnesium deposition-dissolution efficiency, and particularly high tolerance to water and impurities, which significantly reduces the cost of the electrolyte, simplifies the electrolyte preparation process, provides great convenience for the storage and use of the electrolyte, and contributes to the commercialization of rechargeable magnesium batteries.

Description

Technical Field

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

[0002] Rechargeable magnesium batteries have the advantages of high safety, abundant reserves of raw magnesium, and high volumetric capacity. They are considered to be one of the most promising new energy storage technologies in the "post-lithium-ion battery era". As the core component of rechargeable magnesium batteries, the electrolyte has an important impact on the performance of the battery. The electrolyte of a rechargeable magnesium battery is mainly composed of an organic solvent and an electrolyte salt. Similar to the electrolyte of rechargeable lithium or sodium (ion) batteries, the electrolyte of a rechargeable magnesium battery is very sensitive to water and impurities. The presence of trace amounts of water and impurities will seriously affect the performance of the battery. Therefore, the preparation of the electrolyte of a rechargeable magnesium battery requires the organic solvent to be anhydrous and oxygen-free in advance and the use of anhydrous high-purity electrolyte salts as raw materials, which results in high electrolyte costs, cumbersome and lengthy preparation processes, and inconveniences in the storage and use of the electrolyte, becoming a serious obstacle to the development and commercial application of rechargeable magnesium batteries.

[0003] The research and development of rechargeable magnesium battery electrolytes with high tolerance to water and impurities, high conductivity, low overpotential, and high magnesium deposition-dissolution efficiency can not only ensure the excellent performance of the electrolyte and the battery, but also significantly reduce the cost of the electrolyte, simplify the preparation process of the electrolyte, and facilitate the storage and use of the electrolyte. This is bound to play an important role in promoting the development and commercial application of rechargeable magnesium batteries. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a composite rechargeable magnesium battery electrolyte having a high tolerance to water and impurities.

[0005] The invention also provides a method for preparing the composite rechargeable magnesium battery electrolyte.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A composite rechargeable magnesium battery electrolyte, characterized in that it contains an organic solvent, an electrolyte salt and an additive, the total molar concentration of the electrolyte salt in the organic solvent is 1.1-1.5 mol / L, and the total mass percentage concentration of the additive in the organic solvent is 0.5-2.0 wt%.

[0008] Furthermore, the organic solvent is composed of a chain ether organic solvent and a perfluoroamine organic solvent in a volume ratio of 1:0.25 to 1; the electrolyte salt is composed of an organic magnesium salt and an inorganic sodium salt in a molar ratio of 1:0.5 to 1; and the additive is composed of a metal organic framework substance and a hydroxyalkyl cellulose substance in a mass ratio of 1:1 to 3.

[0009] Furthermore, the chain ether organic solvent is any one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; the perfluoroamine organic solvent is any one of perfluorotriethylamine or perfluorotributylamine.

[0010] Furthermore, the organic magnesium salt in the electrolyte salt is any one of magnesium trifluoromethanesulfonate and bis(trifluoromethanesulfonyl imide)magnesium; and the inorganic sodium salt in the electrolyte salt is any one of sodium fluoride and sodium bromide.

[0011] Furthermore, the metal organic framework substance in the additive is any one of ZIF-8 or ZIF-67; the hydroxyalkyl cellulose substance in the additive is any one of hydroxyethyl cellulose or hydroxypropyl cellulose.

[0012] The present invention also provides a method for preparing a composite rechargeable magnesium battery electrolyte, comprising the following steps:

[0013] Prepare the materials according to the above components; under an inert atmosphere at room temperature, measure a chain ether organic solvent and a perfluoroamine organic solvent, mix the two evenly to obtain a composite organic solvent; weigh an organic magnesium salt, an inorganic sodium salt, a metal organic framework additive and a hydroxyalkyl cellulose additive, slowly add them to the composite organic solvent in sequence, and stir magnetically for 48 hours to 60 hours to obtain an electrolyte.

[0014] Furthermore, the raw organic solvent, electrolyte salt and additive do not need to be pre-treated for removing water or impurities.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The composite rechargeable magnesium battery electrolyte of the present invention contains dual organic solvents, dual electrolyte salts and dual additives; the dual organic solvents composed of chain ether solvents and perfluoroamine solvents can not only adjust the polarity of the solvent and increase the solubility of the electrolyte salt, but also enhance the stability of the electrolyte; the dual electrolyte salts composed of organic magnesium salts and inorganic sodium salts can not only increase the concentration of the electrolyte salt and improve the conductivity of the electrolyte, but also help to improve the solvation environment of magnesium ions, promote charge transfer at the electrode-electrolyte interface, reduce the overpotential of magnesium deposition-dissolution and improve the cycle stability; the dual additives composed of metal organic framework substances and hydroxyalkyl cellulose substances can effectively prevent water and impurities from approaching the electrode-electrolyte interface region based on confinement and adsorption effects, thereby ensuring the stability of the interface.

[0017] 2. The synergistic effect between the components of the composite electrolyte of the present invention gives the electrolyte the characteristics of high conductivity, low overpotential, and high magnesium deposition-dissolution efficiency, especially high tolerance to water and impurities, which significantly reduces the cost of the electrolyte, simplifies the electrolyte preparation process, provides great convenience for the storage and use of the electrolyte, and has good application prospects.

[0018] 3. The preparation of the composite rechargeable magnesium battery electrolyte of the present invention does not require any water removal and impurity removal pretreatment of the raw materials, and is only prepared by stirring at room temperature. The process is simple and easy to be mass-produced industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The electrochemical impedance spectroscopy result of the electrolyte prepared in Example 1 of the present invention.

[0020] Figure 2 The cyclic voltammetry curve of the electrolyte prepared in Example 1 of the present invention using molybdenum foil as the working electrode.

[0021] Figure 3 The electrolyte prepared in Example 1 of the present invention uses molybdenum foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of magnesium reversible deposition-stripping at different current densities. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific embodiments.

[0023] 1. A composite rechargeable magnesium battery electrolyte and its preparation method

[0024] Embodiment 1:

[0025] A composite rechargeable magnesium battery electrolyte, the preparation method of which is as follows:

[0026] Under an inert atmosphere at room temperature, 80 mL of ethylene glycol dimethyl ether and 20 mL of perfluorotriethylamine were measured respectively, and the two were mixed evenly to obtain a composite organic solvent; 32.244 g of magnesium trifluoromethanesulfonate, 2.100 g of sodium fluoride, 0.520 g of ZIF-8, and 1.560 g of hydroxyethyl cellulose were weighed respectively, and slowly added into the above composite organic solvent in sequence, and magnetically stirred for 48 hours to obtain a composite rechargeable magnesium battery electrolyte.

[0027] The above raw materials are used directly after purchase without any pretreatment of removing water or impurities.

[0028] Embodiment 2-4:

[0029] The composite rechargeable magnesium battery electrolyte was prepared by the same method as in Example 1, namely comprising the following steps:

[0030] Under an inert atmosphere at room temperature, a certain volume of a chain ether organic solvent and a perfluoroamine organic solvent are measured respectively, and the two are mixed evenly to obtain a composite organic solvent; a certain mass of an organic magnesium salt, an inorganic sodium salt, a metal organic framework additive and a hydroxyalkyl cellulose additive are weighed respectively, and are slowly added to the above composite organic solvent in turn, and magnetic stirring is performed for a certain period of time to obtain a composite rechargeable magnesium battery electrolyte.

[0031] All raw materials are used directly after purchase without any pretreatment for removing water or impurities.

[0032] The preparation conditions of the electrolyte of Example 2-4 (based on 100 mL) are shown in Table 1 below:

[0033] Table 1

[0034]

[0035] 2. Performance test method of the composite rechargeable magnesium battery low temperature electrolyte

[0036] a. Conductivity test of electrolyte

[0037] The conductivity of the electrolyte was obtained by analyzing the electrochemical impedance spectroscopy at the open circuit potential. The electrochemical impedance spectroscopy test was completed using an Autolab PGSTAT302N electrochemical workstation. A three-electrode system was used, with a clean stainless steel foil (14 mm thick) as the reference electrode, working electrode, and counter electrode. The applied excitation signal was 5 mV, and the test frequency range was 10 5 Hz~0.01Hz, the test temperature is room temperature. The electrolyte bulk resistance R is obtained from the measured impedance spectrum s (Ω), and then the electrolyte conductivity (σ, S / cm) is obtained by the following conductivity definition formula:

[0038] σ=l / SR s

[0039] Where l is the thickness of the electrolyte, cm; S is the contact area between the electrolyte and the electrode, cm 2 .

[0040] b. Magnesium reversible deposition-dissolution performance test of electrolyte

[0041] The reversible deposition-dissolution performance of magnesium in the electrolyte was tested by cyclic voltammetry using an Autolab PGSTAT302N electrochemical workstation. A clean magnesium sheet electrode was used as the reference electrode and counter electrode, and a molybdenum foil was used as the working electrode. The potential range was -0.8 to 1.8 V, and the scan rate was 25 mV / s.

[0042] c. Magnesium reversible deposition-dissolution coulombic efficiency test

[0043] The reversible deposition-dissolution coulombic efficiency of magnesium in the electrolyte was tested by assembling a CR2032 button cell. The assembly was carried out in an inert atmosphere glove box. The working electrode was a clean molybdenum foil, the counter electrode was a clean magnesium sheet (also used as a reference electrode), the diaphragm was a GF / A membrane, and the CR2032 button cell was assembled with a homemade electrolyte. After the battery was assembled, it was left to stand at room temperature for 12 hours, and then a constant current charge and discharge test was performed using a Neware instrument with a current density of 0.5 mA cm -2 , discharge for 60 min, then charge to 0.8 V (vs. Mg / Mg 2+ ), and the coulombic efficiency is calculated from the ratio of the charge of deposited magnesium to the charge of dissolved magnesium in one cycle.

[0044] like Figure 1 The electrochemical impedance spectroscopy result of the electrolyte prepared in Example 1 is shown in FIG. 1 . The conductivity of the electrolyte is 5.24 mS·cm -1 The conductivity of the electrolyte of rechargeable magnesium batteries reported in the literature is generally lower than 5.0 mS·cm -1 , indicating that the electrolyte has the characteristic of high conductivity.

[0045] like Figure 2 As shown, with molybdenum foil as the working electrode, the overpotential of the electrolyte after 150 cycles is 127 mV, indicating that the electrolyte has the characteristic of small magnesium deposition-dissolution overpotential.

[0046] like Figure 3 As shown, the coulombic efficiency of magnesium reversible deposition-stripping (on a molybdenum foil substrate) of the electrolyte is maintained at 98.2% when the electrolyte is cycled for 1000 cycles for a long time, indicating that the electrolyte has the characteristic of high magnesium deposition-stripping efficiency.

[0047] Similarly, the electrolyte prepared in Examples 2-4 was tested for performance using the above method, and the results are shown in Table 2. It is further confirmed that the electrolyte of the present invention has the characteristics of high conductivity, low overpotential, and high magnesium deposition-dissolution efficiency.

[0048] Table 2

[0049]

[0050] In summary, the composite rechargeable magnesium battery electrolyte prepared by the present invention has the characteristics of high conductivity, low overpotential, high magnesium deposition-dissolution efficiency, and especially high tolerance to water and impurities, which significantly reduces the cost of the electrolyte, simplifies the electrolyte preparation process, provides great convenience for the storage and use of the electrolyte, and has good commercial application prospects. In addition, the preparation of the electrolyte of the present invention does not require any water removal and impurity removal pretreatment of the raw materials, and is only prepared by stirring at room temperature, which is simple in process and easy to be mass-produced industrially.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A composite rechargeable magnesium battery electrolyte, characterized in that: Containing an organic solvent, an electrolyte salt and an additive, wherein the total molar concentration of the electrolyte salt in the organic solvent is 1.1-1.5 mol / L, and the total mass percentage concentration of the additive in the organic solvent is 0.5-2.0 wt%; The organic solvent is composed of a chain ether organic solvent and a perfluoroamine organic solvent in a volume ratio of 1:0.25-1; the electrolyte salt is composed of an organic magnesium salt and an inorganic sodium salt in a substance amount ratio of 1:0.5-1; the additive is composed of a metal organic framework substance and a hydroxyalkyl cellulose substance in a mass ratio of 1:1-3; the chain ether organic solvent is any one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; the perfluoroamine organic solvent is any one of perfluorotriethylamine or perfluorotributylamine; the organic magnesium salt in the electrolyte salt is any one of magnesium trifluoromethanesulfonate or bis(trifluoromethanesulfonylimide) magnesium; the inorganic sodium salt in the electrolyte salt is any one of sodium fluoride or sodium bromide; the metal organic framework substance in the additive is any one of ZIF-8 or ZIF-67; the hydroxyalkyl cellulose substance in the additive is any one of hydroxyethyl cellulose or hydroxypropyl cellulose.

2. A method for preparing a composite rechargeable magnesium battery electrolyte, characterized in that: The steps include: Prepare the components according to claim 1; under room temperature and inert atmosphere, measure a chain ether organic solvent and a perfluoroamine organic solvent, mix the two uniformly to obtain a composite organic solvent; weigh an organic magnesium salt, an inorganic sodium salt, a metal organic framework additive and a hydroxyalkyl cellulose additive, and slowly add them to the composite organic solvent in sequence, and stir magnetically for 48 h to 60 h to obtain an electrolyte.

3. The method for preparing the composite rechargeable magnesium battery electrolyte according to claim 2, characterized in that: The organic solvent, electrolyte salt and additives used in the preparation do not need any water removal and impurity removal pretreatment.

Images