CN115084652A - A composite rechargeable magnesium battery electrolyte and preparation method thereof - Google Patents

Abstract

The invention provides a composite rechargeable magnesium battery electrolyte and a preparation method thereof. The electrolyte contains an organic solvent, electrolyte salt and an additive; in the preparation process, the raw materials are not subjected to any water removal and impurity removal pretreatment, and are directly stirred and uniformly mixed under the inert atmosphere at room temperature to obtain the electrolyte. The composite electrolyte has the advantages of high conductivity, small overpotential, high magnesium deposition-dissolution efficiency and high tolerance to water and impurities, obviously reduces the cost of the electrolyte, simplifies the preparation process of the electrolyte, provides great convenience for the storage and use of the electrolyte, and is beneficial to commercialization of rechargeable magnesium batteries.

Description

A composite rechargeable magnesium battery electrolyte and preparation method thereof

technical field

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 technique

Rechargeable magnesium batteries have the advantages of high safety, abundant raw material magnesium reserves, and high volume specific capacity, and 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 rechargeable magnesium battery is mainly composed of organic solvent and electrolyte salt. Similar to electrolytes such as rechargeable lithium or sodium (ion) batteries, rechargeable magnesium battery electrolytes are very sensitive to water and impurities, and the presence of trace amounts of water and impurities can seriously affect battery performance. Therefore, the preparation of the electrolyte for rechargeable magnesium batteries requires anhydrous and oxygen-free treatment of the organic solvent in advance and the use of anhydrous high-purity electrolyte salts as raw materials, which results in high cost of the electrolyte, cumbersome and lengthy preparation process, and also reduces the storage and storage of the electrolyte. The inconvenience caused by the use has become a serious obstacle to the development and commercial application of rechargeable magnesium batteries.

The research and development of rechargeable magnesium battery electrolyte with high conductivity, low overpotential and high magnesium deposition-dissolution efficiency with high tolerance to water and impurities can not only ensure the excellent performance of the electrolyte and the battery, but also significantly reduce the electrolyte's performance. Cost, simplifying the preparation process of the electrolyte, and facilitating the storage and use of the electrolyte are bound to play an important role in promoting the development and commercial application of rechargeable magnesium batteries.

SUMMARY OF THE INVENTION

In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a composite type rechargeable magnesium battery electrolyte with high tolerance to water and impurities.

The present invention also provides a method for preparing the electrolyte for the composite rechargeable magnesium battery.

To achieve the above object, the present invention adopts the following technical solutions:

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 additive is in the organic solvent. The total mass percentage concentration in 0.5-2.0 wt%.

Further, 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 ratio of 1:0. The additive is composed of metal organic framework substances and hydroxyalkyl cellulose substances in a mass ratio of 1:1 to 3.

Further, 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 fluorine amine organic solvent is any one of perfluorotriethylamine or perfluorotributylamine.

Further, the organic magnesium salt in the electrolyte salt is any one of magnesium trifluoromethanesulfonate or magnesium bis(trifluoromethanesulfonimide); the inorganic sodium salt in the electrolyte salt is sodium fluoride or Any of sodium bromide.

Further, 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 hydroxyethyl cellulose or hydroxypropyl cellulose any of the .

The present invention also provides a preparation method of a composite rechargeable magnesium battery electrolyte, comprising the following steps:

Prepare the materials according to the above components; under an inert atmosphere at room temperature, measure the chain ether organic solvent and the perfluoroamine organic solvent, and mix the two evenly to obtain a composite organic solvent; weigh the organic magnesium salt, inorganic sodium salt, metal Organic framework additives and hydroxyalkyl cellulose additives are slowly added to the composite organic solvent in turn, and magnetically stirred for 48h to 60h to obtain an electrolyte.

Further, the raw material organic solvent, electrolyte salt and additives do not need any pretreatment for water removal and impurity removal.

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

1. The electrolyte of the composite rechargeable magnesium battery of the present invention contains dual organic solvents, dual electrolyte salts and dual additives; the dual organic solvents composed of chain ether solvents and perfluorinated amine solvents can not only adjust the polarity of the solvent, increase the The solubility of the large electrolyte salt can also enhance the stability of the electrolyte; the double electrolyte salt composed of organic magnesium salts and inorganic sodium salts can not only increase the concentration of the electrolyte salt, improve the conductivity of the electrolyte, but also help to improve magnesium ions. solvation environment, promoting charge transfer at the electrode-electrolyte interface, reducing magnesium deposition-dissolution overpotential, and improving cycling stability; dual additives composed of metal-organic frameworks and hydroxyalkylcelluloses are based on confinement The adsorption effect can effectively prevent water and impurities from approaching the electrode-electrolyte interface area, ensuring the stability of the interface.

2. The synergistic effect between the components of the composite electrolyte of the present invention endows the electrolyte with the characteristics of large electrical conductivity, small overpotential, and high magnesium deposition-dissolution efficiency, especially with high tolerance to water and impurities, This significantly reduces the cost of the electrolyte, simplifies the preparation process of the electrolyte, provides great convenience for the storage and use of the electrolyte, and has good application prospects.

3. The preparation of the composite rechargeable magnesium battery electrolyte of the present invention does not require any dewatering and impurity pretreatment of the raw materials, and only adopts the stirring method at room temperature, the process is simple, and the large-scale industrial production is easy.

Description of drawings

FIG. 1 is the electrochemical impedance spectroscopy result of the electrolyte prepared in Example 1 of the present invention.

Fig. 2 is the cyclic voltammetry curve of the electrolyte prepared in Example 1 of the present invention using molybdenum foil as the working electrode.

FIG. 3 shows the reversible deposition-dissolution Coulomb efficiency of magnesium in the electrolyte prepared in Example 1 of the present invention with molybdenum foil as the working electrode at a current density of 0.5 mA·cm ^-2 .

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments.

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

Example 1:

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

Under an inert atmosphere at room temperature, weigh 80 mL of ethylene glycol dimethyl ether and 20 mL of perfluorotriethylamine respectively, and mix the two evenly to obtain a composite organic solvent; weigh 32.244 g of magnesium trifluoromethanesulfonate, 2.100 g of fluorinated trifluoromethanesulfonate, respectively. Sodium, 0.520g ZIF-8, and 1.560g hydroxyethyl cellulose were slowly added to the above-mentioned composite organic solvent in turn, and magnetically stirred for 48 hours to obtain a composite rechargeable magnesium battery electrolyte.

The above raw materials are used directly after purchase, without any pretreatment of water removal and impurity removal.

Example 2-4:

The composite rechargeable magnesium battery electrolyte is prepared by the same method as in Example 1, including the following steps:

Under an inert atmosphere at room temperature, measure a certain volume of a chain ether-based organic solvent and a perfluoroamine-based organic solvent, and mix the two evenly to obtain a composite organic solvent; respectively weigh a certain mass of organic magnesium salt, inorganic sodium salt, The metal organic framework additives and the hydroxyalkyl cellulose additives are slowly added to the above-mentioned composite organic solvent in turn, and magnetically stirred for a certain period of time to obtain a composite type rechargeable magnesium battery electrolyte.

All raw materials are used directly after purchase, without any pretreatment of water removal and impurity removal.

The electrolyte (in 100mL) preparation condition of embodiment 2-4 is as shown in Table 1 below:

Table 1

2. Performance test method for the low-temperature electrolyte of the composite rechargeable magnesium battery

a. Conductivity test of electrolyte

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

σ=l/SR _s

where l is the thickness of the electrolyte, cm; S is the contact area between the electrolyte and the electrode, cm ² .

b. Magnesium reversible deposition-dissolution performance test of electrolyte

The magnesium reversible deposition-dissolution properties of the electrolyte were tested by cyclic voltammetry using an Autolab PGSTAT302N electrochemical workstation. The clean magnesium sheet electrode was used as the reference electrode and the counter electrode, and the molybdenum foil was used as the working electrode. The potential range was -0.8~1.8V, and the scanning speed was 25mV/s.

c. Magnesium reversible deposition-dissolution coulombic efficiency test

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

As shown in FIG. 1 , which is the electrochemical impedance spectrum result of the electrolyte prepared in Example 1, it can be obtained that the conductivity of the electrolyte is 5.24 mS·cm ⁻¹ by analyzing it. However, the conductivity of the electrolyte for rechargeable magnesium batteries reported in the literature is generally lower than 5.0mS·cm ^-1 , indicating that the electrolyte has the characteristics of high conductivity.

As shown in Figure 2, with molybdenum foil as the working electrode, the overpotential of the electrolyte after 150 cycles of circulation is 127mV, indicating that the electrolyte has the characteristics of small magnesium deposition-dissolution overpotential.

As shown in Fig. 3, the reversible magnesium deposition-dissolution (on molybdenum foil substrate) Coulomb efficiency of the electrolyte maintained at 98.2% when the electrolyte was cycled for 1000 cycles, indicating that the electrolyte has the characteristics of high magnesium deposition-dissolution efficiency.

Similarly, the electrolyte solutions prepared in Examples 2-4 were 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 electrical conductivity, low overpotential and high magnesium deposition-dissolution efficiency.

Table 2

To sum up, the composite type rechargeable magnesium battery electrolyte prepared by the present invention has the characteristics of high electrical conductivity, low overpotential, high magnesium deposition-dissolution efficiency, especially high tolerance to water and impurities, which significantly reduces the The cost of the electrolyte solution simplifies the preparation process of the electrolyte solution, provides great convenience for the storage and use of the electrolyte solution, and has good commercial application prospects. In addition, the preparation of the electrolyte of the present invention does not require any pretreatment of dewatering and impurity removal on the raw materials, and only adopts a stirring method at room temperature to prepare the electrolyte, and the process is simple and easy for large-scale industrial production.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that those technical solutions of the present invention are modified or equivalently replaced without departing from the present technology. The purpose and scope of the solution should be included in the scope of the claims of the present invention.

Claims (7)

1. a composite type rechargeable magnesium battery electrolyte, is characterized in that, contains organic solvent, electrolyte salt and additive, the total molar concentration of described electrolyte salt in organic solvent is 1.1～1.5 mol/L, and described additive is in 1.1～1.5 mol/L. The total mass percentage concentration in the organic solvent is 0.5~2.0 wt%. 2. The composite type rechargeable magnesium battery electrolyte according to claim 1, wherein 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 organic magnesium salts and inorganic sodium salts in a ratio of 1:0.5 to 1; the additives are composed of metal organic framework substances and hydroxyalkyl cellulose substances in a mass ratio of 1:1 to 3. . 3. The composite type rechargeable magnesium battery electrolyte according to claim 2, wherein the chain ether organic solvent is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol diethyl ether Any one of methyl ether and tetraethylene glycol dimethyl ether; the perfluoroamine organic solvent is any one of perfluorotriethylamine or perfluorotributylamine. 4. The electrolyte of the composite rechargeable magnesium battery according to claim 2, wherein the organic magnesium salt in the electrolyte salt is in magnesium trifluoromethanesulfonate or magnesium bis(trifluoromethanesulfonimide) any one; the inorganic sodium salt in the electrolyte salt is any one in sodium fluoride or sodium bromide. 5. The electrolyte for composite rechargeable magnesium battery according to claim 2, wherein the metal organic framework substance in the additive is any one of ZIF-8 or ZIF-67; The hydroxyalkyl cellulose material is any one of hydroxyethyl cellulose or hydroxypropyl cellulose. 6. a preparation method of composite rechargeable magnesium battery electrolyte, is characterized in that, comprises the steps: Prepare materials according to any one of claims 1 to 5; under an inert atmosphere at room temperature, measure a chain ether organic solvent and a perfluoroamine organic solvent, and mix the two evenly to obtain a composite organic solvent; weigh the organic magnesium salt, Inorganic sodium salt, metal organic framework additives and hydroxyalkyl cellulose additives are slowly added to the composite organic solvent in turn, and magnetically stirred for 48 h to 60 h to obtain an electrolyte. 7 . The method for preparing a composite rechargeable magnesium battery electrolyte according to claim 6 , wherein the organic solvent, electrolyte salt and additives used in the preparation do not require any pretreatment for water removal and impurity removal. 8 .

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