An electrolyte for a magnesium rechargeable battery with a wide potential window and a preparation method thereof

Abstract

The present invention provides an electrolyte for a rechargeable magnesium battery with a wide potential window and a preparation method thereof. The electrolyte of the present invention uses two types of organic magnesium salts (Type I and Type II), two types of organic solvents (Type A and Type B), and an additive as raw materials. The preparation method is that under an inert atmosphere at room temperature, the Type I organic magnesium salt in the above raw materials is added to the Type A organic solvent and stirred for 8 to 12 hours, then the Type B organic solvent is added thereto and stirred for 2 to 4 hours, then the Type II organic magnesium salt is added and stirred for 20 to 24 hours, and finally the additive is added and stirred for 1 to 3 hours to obtain the electrolyte of the present invention. The electrolyte of the present invention has a large conductivity, a small overpotential, and a high magnesium deposition-dissolution efficiency. In particular, it has a wide electrochemical window and an oxidation stability window as high as more than 4V (vs. Mg / Mg<supgt;2+< / supgt>). Therefore, it is suitable for matching high-voltage cathode materials to form high-performance rechargeable magnesium batteries and has important popularization and application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of rechargeable magnesium batteries, and particularly relates to an electrolyte for a rechargeable magnesium battery with a wide potential window and a preparation method thereof. Background Art

[0002] As one of the current most advanced electrochemical energy storage technologies, lithium-ion batteries are widely used in multiple fields. However, problems such as poor safety and high cost have increasingly attracted people's attention. Therefore, it is imperative to develop new electrochemical energy storage technologies with high safety and low cost. Rechargeable magnesium batteries are considered the most promising new energy storage technologies to replace lithium due to their high volumetric specific capacity, high safety, and abundant raw material magnesium reserves, and have attracted more attention in recent years.

[0003] As an important component of the battery, the electrolyte has an important impact on the performance of the battery. Currently, the electrolytes for rechargeable magnesium batteries mainly include APC electrolyte PhMgCl / AlCl 3 / THF, hexamethyldisilazide alkyl electrolyte (HMDS) 2 Mg / AlCl 3 / THF, inorganic magnesium chloride-based electrolyte MgCl 2 / AlCl 3 / Mg / DME (MACC), magnesium bis(trifluoromethanesulfonyl)imide electrolyte Mg(TFSI) 2 / THF and Mg(TFSI) 2 / MgCl 2 / DME, boron-based electrolyte Mg[B(hfip) 4 2 / DME, etc. These electrolytes can all achieve reversible deposition-dissolution of magnesium, but usually have a narrow electrochemical window, and it is very difficult to break through 4V (vs. Mg / Mg 2+ ) for the oxidation stability window, which causes some high-voltage cathode materials to be difficult to be applied in rechargeable magnesium batteries, seriously hindering the development of high-performance rechargeable magnesium batteries. Therefore, it is urgent to develop an electrolyte for a rechargeable magnesium battery with a wide potential window to match high-voltage cathode materials and thus obtain a high-performance rechargeable magnesium battery. Summary of the Invention

[0004] Aiming at the above deficiencies existing in the prior art, the purpose of the present invention is to provide an electrolyte for a rechargeable magnesium battery with a wide potential window, and solve the problem that the electrochemical window of the existing electrolytes for rechargeable magnesium batteries is narrow and the oxidation stability window is very difficult to break through 4V (vs. Mg / Mg 2+ ).

[0005] The present invention also provides a preparation method of the above electrolyte.

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

[0007] A wide potential window rechargeable magnesium battery electrolyte, characterized in that it contains a double organic magnesium salt, a double organic solvent and an additive; its oxidation stability potential window is not less than 4V (vs. Mg / Mg 2+ ).

[0008] Furthermore, the total molar concentration of the double organic magnesium salt in the double organic solvent is 0.6 to 1.0 mol / L, and the molar concentration of the additive in the double organic solvent is 0.0001 to 0.0005 mol / L.

[0009] The double organic magnesium salt is a type I organic boron magnesium salt and a type II organic aluminum magnesium salt; the double organic solvent is an A-type chain ether solvent and a B-type fluorinated ether solvent.

[0010] The additive is a sulfonamide substance, including one or two of sulfacetamide, sulfadiazine, and sulfisoxazole.

[0011] Furthermore, the amount of substance of the type I organic boron magnesium salt is 5 to 9 times the amount of substance of the type II organic aluminum magnesium salt; the volume of the A-type chain ether solvent is 9 to 19 times the volume of the B-type fluorinated ether solvent.

[0012] Among them, the type I organic boron magnesium salt includes one or two of magnesium bis(trifluoroethyl)borate, magnesium tetra(trifluoromethoxy)borate, and magnesium hexafluoroisopropyl borate. The type II organic aluminum magnesium salt includes one or two of magnesium tetrafluorotert-butyl aluminate, magnesium tetra(perfluorotert-butoxy) aluminate, and magnesium hexafluoroisopropyl aluminate.

[0013] The A-type chain ether solvent is one or two of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The B-type fluorinated ether solvent is one or two of perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, perfluorobutyl methyl ether, and tetrafluoroethyl butyl ether.

[0014] The present invention also provides a preparation method of a wide potential window rechargeable magnesium battery electrolyte, characterized by including the following steps:

[0015] According to the components of the wide potential window rechargeable magnesium battery electrolyte above, take a type I organic magnesium salt, a type II organic magnesium salt, an A-type organic solvent, a B-type organic solvent and an additive; under an inert atmosphere at room temperature, add the type I organic magnesium salt to the A-type organic solvent and stir for 8 to 12 h, then add the B-type organic solvent thereto and stir for 2 to 4 h, then add the type II organic magnesium salt and stir for 20 to 24 h, and finally add the additive and stir for 1 to 3 h to obtain the electrolyte.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The electrolyte components of the present invention include double organic magnesium salts, double organic solvents and sulfonamide additives; among them, the magnesium salt is the provider of Mg in the electrolyte and is a key component for realizing reversible magnesium deposition-dissolution in the electrolyte. The double organic magnesium salts (organic boron magnesium salt and organic aluminum magnesium salt) in the present invention do not contain halogen ions and do not corrode the negative magnesium metal and the positive current collector material, and can provide more effective active cations, increase the conductivity of the electrolyte, improve the reversible deposition-dissolution performance of magnesium in the electrolyte, and reduce the overpotential. The double organic solvents (chain ether solvents and fluorinated ether solvents) can not only increase the solubility of the organic magnesium salt, but also adjust the solvation structure formed by the solvent molecules and magnesium ions, reduce the overpotential, accelerate the desolvation process, and improve the kinetics. The sulfonamide additive can effectively inhibit the formation of a passivation layer on the surface of the magnesium anode and improve the cycle stability of the electrolyte. 2+

[0018] 2. The synergistic effect among the components of the electrolyte of the present invention endows the electrolyte with high conductivity, small overpotential, and high magnesium deposition-dissolution efficiency. In particular, it has a wide electrochemical window and an oxidation stability window as high as 4V (vs. Mg / Mg 2+ ), which is suitable for matching with high-voltage cathode materials to form high-performance rechargeable magnesium batteries and has important popularization and application value.

[0019] 3. The preparation process of the electrolyte for the rechargeable magnesium battery with a wide potential window of the present invention is carried out at room temperature and only adopts a stirring treatment method. The preparation process is simple and is easy to be industrially produced on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a magnesium deposition-dissolution curve of the electrolyte prepared in Example 1 of the present invention studied by cyclic voltammetry.

[0021] Figure 2 It is the result of the oxidation stability of the electrolyte prepared in Example 1 of the present invention on the common positive current collector material stainless steel foil studied by linear voltammetry. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be further described in detail below with reference to specific examples.

[0023] I. An electrolyte for a rechargeable magnesium battery with a wide potential window and its preparation method

[0024] Example 1:

[0025] An electrolyte for a rechargeable magnesium battery with a wide potential window, and its preparation method is as follows:

[0026] ​1.3050 g of magnesium hexafluoroisopropyl borate was added to 9.5 mL of ethylene glycol dimethyl ether solvent and stirred for 10 h. Then, 0.5 mL of tetrafluoroethyl butyl ether was added thereto and stirred for 3 h. Next, 0.2740 g of magnesium tetrafluorotert-butyl aluminate was added and stirred for 24 h. Finally, 0.0005 g of sulfadiazine was added and stirred for 3 h to obtain the electrolyte.

[0027] The above reactions were all carried out under an inert atmosphere at room temperature, and the water and oxygen contents were both lower than 0.01 ppm.

[0028] Examples 2-5 were prepared by the same method as Example 1 to obtain a wide potential window rechargeable magnesium battery electrolyte, which included the following steps:

[0029] All reactions were carried out under an inert atmosphere at room temperature, and the water and oxygen contents were both lower than 0.01 ppm. Take Class I organic magnesium salt, Class II organic magnesium salt, Solvent A, Solvent B and additive. Add the Class I organic magnesium salt to Solvent A and stir for a certain time t 1 , then add Solvent B thereto and stir for a certain time t 2 , then add the Class II organic magnesium salt and stir for a certain time t 3 , and finally add the additive and stir for a certain time t 4 to obtain the electrolyte.

[0030] The preparation raw materials and their dosages in Examples 2-5 are as follows:

[0031]

[0032]

[0033] The stirring time for each step in Examples 2-5 is as follows:

[0034] Example <![CDATA[t 1 / h]]> <![CDATA[t 2 / h]]> <![CDATA[t 3 / h]]> <![CDATA[t 4 / h]]> Example 2 12 4 20 2 Example 3 8 2 22 1 Example 4 11 3 21 2 Example 5 9 3 23 3

[0035] II. Performance test method for the wide potential window rechargeable magnesium battery electrolyte

[0036] a. Reversible magnesium deposition-dissolution performance and oxidation stability window test

[0037] The reversible magnesium deposition-dissolution performance and oxidation stability window of the electrolyte were tested by cyclic voltammetry and linear sweep voltammetry respectively, and completed using an Autolab PGSTAT302N electrochemical workstation. A clean magnesium sheet electrode was used as the reference electrode and counter electrode, and a stainless steel current collector was used as the working electrode. For cyclic voltammetry testing, the potential range was -0.8 to 4.5 V, and the scan rate was 25 mV / s. For linear sweep voltammetry testing, the potential range was from the open circuit potential to 5.0 V, and the scan rate was 1 mV / s.

[0038] b. Conductivity Test

[0039] The conductivity of the electrolyte is obtained by analyzing the electrochemical impedance spectrum. The electrochemical impedance spectrum test is carried out in an inert atmosphere glove box and completed using an Autolab PGSTAT302N electrochemical workstation. A clean stainless-steel electrode is used as the reference electrode, working electrode, and counter electrode. The applied excitation signal is 5 mV, and the test frequency range is 10 5 Hz to 0.01 Hz, and the test temperature is 25 °C. The bulk resistance R s (Ω) of the electrolyte is obtained from the measured impedance spectrum, and then the conductivity (σ, S / cm) of the electrolyte is obtained through the following definition formula of conductivity:

[0040] σ = l / SR s

[0041] where l is the thickness of the electrolyte, cm; S is the contact area between the electrolyte and the electrode, cm 2 .

[0042] c. Coulombic Efficiency Test of Reversible Magnesium Deposition-Dissolution

[0043] The reversible deposition-dissolution coulombic efficiency of magnesium in the electrolyte is tested by assembling a CR2032 coin cell. The assembly is carried out in an inert atmosphere glove box with the water and oxygen contents both less than 0.01 ppm. The working electrode is a clean stainless-steel (SS) foil, the counter electrode uses a clean magnesium sheet (also as the reference electrode), the separator uses a GF / A membrane, and it is assembled with the self-made electrolyte into a CR2032 coin cell. After the battery is assembled, it is left standing at room temperature for 12 hours before measurement. The whole test process is carried out on a Wuhan Blue Electric (Land) charge-discharge test system. During discharge (1 hour), the deposition reaction of magnesium occurs on the working electrode, and the current density is 0.1 - 0.5 mAcm -2 ; during the charging process, it is the dissolution reaction of the magnesium deposited on the working electrode, and the current density is 0.1 - 0.5 mAcm -2 , and voltage control is adopted (charged to 0.8 V vs. Mg RE).

[0044] Using the above method to test the performance of the electrolyte prepared in Example 1, the test results are as follows: the overpotential of magnesium deposition-dissolution is 197 mV, and no additional peaks appear in the potential range up to 4.5 V (see Figure 1 ); the oxidation stability potential window of the electrolyte on the common positive current collector material stainless-steel foil is as high as 4.023 V (vs. Mg / Mg 2+ ) (see Figure 2 ); the conductivity of the electrolyte is 4.12 mS·cm -1; The Coulombic efficiency of the reversible magnesium deposition-dissolution (on a stainless steel current collector) of the electrolyte during 200 cycles has been maintained at 98%; the above performance test results indicate that the electrolyte of the present invention has the characteristics of high conductivity, small overpotential, high magnesium deposition-dissolution efficiency, wide electrochemical window, and high stability.

[0045] Similarly, the above method was used to test the performance of the electrolytes prepared in Examples 2-5, and the results are shown in the following table.

[0046]

[0047] It can be seen therefrom that the electrolyte of the present invention has excellent properties such as high conductivity, small overpotential, high magnesium deposition-dissolution efficiency, and wide electrochemical window (all not less than 4V, vs. Mg / Mg 2+ ).

[0048] In summary, the rechargeable magnesium battery electrolyte prepared by the present invention endows the electrolyte with high conductivity, small overpotential, and high magnesium deposition-dissolution efficiency through the synergistic effect among the components. In particular, the electrochemical window is wide, and the oxidation stability window is as high as 4V (vs. Mg / Mg 2+ ), which is suitable for matching with high-voltage cathode materials to form high-performance rechargeable magnesium batteries and has important popularization and application value. Moreover, the preparation process of the electrolyte of the present invention is carried out at room temperature and only adopts the stirring treatment method, and the preparation process is simple and easy to be mass-produced industrially.

[0049] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those of ordinary skill in the art should understand that any modifications or equivalent replacements made to the technical solutions of the present invention without departing from the purpose and scope of the present technical solution should be covered within the scope of the claims of the present invention.

Claims

1. An electrolyte for a magnesium rechargeable battery with a wide potential window, characterized in that, Containing a double-organic magnesium salt, a double-organic solvent and an additive; its oxidation stability potential window is not less than 4 V (vs. Mg / Mg 2+ ). wherein the total molar concentration of the double organic magnesium salt in the double organic solvent is 0.6 - 1.0 mol / L, and the molar concentration of the additive in the double organic solvent is 0.0001 - 0.0005 mol / L; the double organic magnesium salt is a type I organic boron magnesium salt and a type II organic aluminum magnesium salt; the double organic solvent is a type A chain ether solvent and a type B fluorinated ether solvent; the additive is a sulfonamide substance, including one or two of sulfacetamide, sulfadiazine, and sulfisoxazole; the amount of substance of the type I organic boron magnesium salt is 5 - 9 times the amount of substance of the type II organic aluminum magnesium salt; the volume of the type A chain ether solvent is 9 - 19 times the volume of the type B fluorinated ether solvent.

2. The electrolyte for a magnesium rechargeable battery with a wide potential window according to claim 1, characterized in that, the type I organic boron magnesium salt includes one or two of magnesium bis(trifluoroethyl) borate, magnesium tetra(trifluoromethoxy) borate, and magnesium hexafluoroisopropyl borate.

3. The electrolyte for a magnesium rechargeable battery with a wide potential window according to claim 1, characterized in that, the type II organic aluminum magnesium salt includes one or two of magnesium tetrafluorotert-butyl aluminate, magnesium tetra(perfluorotert-butoxy) aluminate, and magnesium hexafluoroisopropyl aluminate.

4. The electrolyte for a magnesium rechargeable battery with a wide potential window according to claim 1, characterized in that, the type A chain ether solvent is one or two of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

5. The electrolyte for a magnesium rechargeable battery with a wide potential window according to claim 1, characterized in that, the type B fluorinated ether solvent is one or two of perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, perfluorobutyl methyl ether, and tetrafluoroethyl butyl ether.

6. A preparation method of an electrolyte for a magnesium rechargeable battery with a wide potential window, characterized in that, comprises the following steps: According to the components of the electrolyte for a magnesium rechargeable battery with a wide potential window as described in any one of claims 1 - 5, take the type I organic magnesium salt, type II organic magnesium salt, type A organic solvent, type B organic solvent, and additive; under an inert atmosphere at room temperature, add the type I organic magnesium salt to the type A organic solvent and stir for 8 - 12 h, then add the type B organic solvent thereto and stir for 2 - 4 h, then add the type II organic magnesium salt and stir for 20 - 24 h, and finally add the additive and stir for 1 - 3 h to obtain the electrolyte.

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