A magnesium battery electrolyte, its preparation method, and the magnesium battery.

Abstract

This invention relates to a magnesium battery electrolyte, its preparation method, and a magnesium battery. The magnesium battery electrolyte comprises a magnesium salt electrolyte, organoboronic acid and its derivatives, an organic ether solvent, and additives. The magnesium battery electrolyte does not contain chlorine-containing compounds. The magnesium salt electrolyte is a non-nucleophilic electrolyte, and the additives are dehydrating additives. This invention also provides a method for preparing the magnesium battery electrolyte, wherein water is removed from the magnesium salt electrolyte, organoboronic acid and its derivatives, organic ether solvent, and additives respectively; under anhydrous and oxygen-free conditions, the magnesium salt electrolyte and organic ether solvent are mixed, and then organoboronic acid and its derivatives and additives are added sequentially under stirring, and the mixture is stirred for 8 to 30 hours to obtain the magnesium battery electrolyte. This invention also provides a magnesium battery in which the electrolyte is the magnesium battery electrolyte described in this invention. This invention solves the problems of narrow electrochemical window and short cycle life in magnesium batteries.

Description

Technical Field

[0001] This invention relates to the field of magnesium battery technology, specifically to a magnesium battery electrolyte, a preparation method, and a magnesium battery. Background Technology

[0002] Today, portable electronic products and electric vehicles place higher demands on energy storage batteries. In recent years, magnesium-ion batteries have gained popularity due to their high volumetric energy density (3832 mAh / cm³). 3 Magnesium batteries have attracted much attention due to their advantages such as negative redox potential (-2.37V vs. SHE), high abundance in the Earth's crust, and good safety, making them an excellent candidate for next-generation energy storage. However, the successful commercialization of rechargeable magnesium batteries faces challenges such as severe passivation of the magnesium anode, slow cathode kinetics, and very low battery power density (<0.5kW kg⁻¹). -1 0.8mW cm -2 The problem is...

[0003] Electrolyte, as the "blood" of a battery, plays a crucial role in its overall performance. In magnesium-ion batteries, the interfacial layer caused by electrolyte decomposition often hinders the growth of magnesium ions. 2+ Diffusion. Therefore, most simple ionic salts that easily form passivation films (such as Mg(ClO4)2 and Mg(BF4)2) and polar aprotic solvents (such as carbonates and nitriles) are not suitable as electrolytes for magnesium-ion batteries.

[0004] In existing magnesium-ion battery electrolyte technologies, nucleophilic electrolytes are compatible with Mg intercalated cathodes, but at room temperature, Mg... 2+ The insertion / extraction is affected by Mg at the electrode / electrolyte interface. 2+ The high energy barrier of desolvation and its low diffusion rate in materials significantly limit their use. Furthermore, nucleophilic components readily react with electrophilic materials, making them unsuitable for organic polymer electrodes and conversion-type cathodes (such as sulfur and iodine). Researchers have extensively explored non-nucleophilic electrolytes, among which bis(diisopropylamino)magnesium (MBA), a common electrolyte component, has attracted considerable attention due to its high coulombic efficiency and low overpotential.

[0005] MBA is an inexpensive non-nucleophilic electrolyte (US$66 / 0.7 mol L). -1(100 mL THF, equivalent to $4.2 / gram) is a promising magnesium salt that can replace existing expensive and difficult-to-prepare magnesium salts, such as Mg(TFSI)2, Mg(HMDS)2, and Mg(B(hfip)4)2 and all-phenyl complexes (APC). However, MBA / THF electrolytes have limited ionic conductivity and a poor electrochemical window, and most existing technologies require the introduction of MgCl2 or AlCl3 to improve this. For example, CN113258138A discloses an all-inorganic salt type rechargeable magnesium battery electrolyte and its preparation method, which adds MgCl2 and Cl-containing compounds to the electrolyte. - Al is a co-solvent and activator. Therefore, the technique of introducing Al-containing Lewis acids (AlCl3, AlEtCl2, and Me2AlCl) has been widely used to improve the compatibility of the negative electrode-electrolyte interface and broaden anode stability. Appropriate amounts of Cl... - It is believed to not only help stabilize Mg 2+ Furthermore, it helps dissolve passivation species on the Mg anode, thereby hindering the formation of the anolyte passivation film and achieving reversible Mg plating / removal. Recently, 1-ethyl-3-methylimidazolium tetrachloroaluminate [C2mim][AlCl4] was first introduced into an MBA-based electrolyte and has been shown to support reversible Mg deposition / dissolution with a coulombic efficiency of 92% on stainless steel (SS). However, the Cl in the electrolyte... - This can lead to a decrease in the efficiency of magnesium deposition cycles. Most importantly, the Cl in the anionic component... - Elements and their associated ligand compounds can cause severe corrosion to common current collectors such as SS, Al, and Cu. Meanwhile, electrolytes inevitably contain trace amounts of moisture and impurities; in the presence of H₂O, free Cl₂... - It will attack the negative electrode metal Mg, thereby reducing the deposition / dissolution coulombic efficiency. Therefore, Cl - The presence of [something] has an extremely adverse effect on the long-term cycle life of the battery, and can eventually lead to battery failure.

[0006] In summary, among existing MBA non-nucleophilic electrolyte technologies, Cl - Introducing MBA-based electrolytes can lead to problems such as a narrow electrochemical window and short cycle life. Therefore, it is necessary to develop an MBA-based electrolyte that is simple to prepare, low in cost, and has a wide electrochemical window to promote the development and commercial application of rechargeable magnesium-ion battery electrolytes. Summary of the Invention

[0007] The purpose of this invention is to provide a magnesium battery electrolyte, a preparation method, and a magnesium battery to solve the problems of narrow electrochemical window and short cycle life of magnesium batteries.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A magnesium battery electrolyte comprises a magnesium salt electrolyte, an organoboric acid and its derivatives, an organic ether solvent, and additives. The magnesium battery electrolyte does not contain chlorine-containing compound additives. The magnesium salt electrolyte is a non-nucleophilic electrolyte, and the additives are dehydrating additives.

[0010] Based on the above technical means, by using a non-nucleophilic electrolyte as the magnesium salt in the magnesium battery electrolyte, and simultaneously using an organic ether solvent as the organic solvent, the magnesium salt exhibits a moderate binding capacity with the organic ether solvent, thereby improving the solubility of the magnesium salt; by adding organic boric acid and its derivatives to the magnesium battery electrolyte, it readily binds with electron-rich substances (such as F... - The combination of materials enhances the Mg 2+ The dissociation of ions with anions effectively improves ionic conductivity and reduces interfacial impedance, thereby accelerating the battery's kinetic process. Using HFE as an additive, its -CF3 content has a strong electron-withdrawing ability, thus suppressing electron loss under high voltage. It also readily combines with electron-deficient organic boric acids and their derivatives, thereby improving anodic oxidation stability. By avoiding the introduction of chlorine-containing compounds into the magnesium battery electrolyte, it is non-corrosive to the current collector and battery casing, thus significantly extending the battery's working life.

[0011] Preferably, the magnesium salt electrolyte is one or more of bis(diisopropylamino)magnesium (MBA), magnesium borohydride, n-butylmagnesium, bis(trifluoromethanesulfonyl)imide magnesium (Mg(TFSI)2), and magnesium trifluoromethanesulfonate.

[0012] Preferably, the magnesium salt electrolyte is bis(diisopropylamino)magnesium (MBA).

[0013] Preferably, the organoboronic acid and its derivatives are one or more of (dimethylbenzylsilane)boronic acid pinacol ester (DPFB), tri(trimethylsilane)boronic acid ester, and β-methoxy-10-trimethylsilyl-9-boronbicyclo(3.3.2)decane.

[0014] Preferably, the organic ether solvent is one or more selected from tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether;

[0015] The additive is decafluoro-3-methoxy-2-trifluoromethylpentane (HFE), 2,2-dimethoxypropane, or a quaternary ammonium salt of borohydride;

[0016] The borohydride quaternary ammonium salt includes one or more of tetramethylammonium borohydride, tetraethylammonium borohydride, and tetrabutylammonium borohydride.

[0017] Preferably, the magnesium salt electrolyte is bis(diisopropylamino)magnesium (MBA); the organoboronic acid and its derivatives are pinacol (dimethylbenzylsilane)borate (DPFB); and the additive is decafluoro-3-methoxy-2-trifluoromethylpentane (HFE).

[0018] Among these, MBA is the preferred magnesium salt electrolyte. This type of magnesium salt has a moderate binding capacity with ether solvents, making it readily soluble in ether solvents such as THF. Furthermore, the raw materials for this type of electrolyte are abundant, inexpensive, and easy to mass-produce.

[0019] In magnesium battery electrolytes, DPTB is an electron-deficient boron compound and anion acceptor, which can prevent the decomposition of anions in the electrolyte. Simultaneously, it readily binds to electron-rich ions (such as Fe). - Material combination to enhance Mg 2+ The dissociation of ions with anions increases ionic conductivity and reduces interfacial impedance, thereby accelerating the battery's kinetics. In the decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) additive used, -CF3 has a strong electron-withdrawing ability. The strong electron-attracting ability of fluorine can suppress electron loss under high voltage and easily combine with the electron-deficient DPTB, thus improving anodic oxidation stability. Furthermore, DPTB can form a thinner cathode-electrolyte interface, which is beneficial for Mg... 2+ The migration of the cathode material inhibits the rapid decay of its capacity.

[0020] Preferably, the molar ratio of the magnesium salt electrolyte to the organoboronic acid and its derivatives is 1:0.5 to 5.

[0021] By rationally adjusting the molar ratio of DPTB to MBA in the magnesium battery electrolyte, high-voltage cycling of the magnesium battery electrolyte can be achieved without the need for expensive B-based components or ionic liquids, or the addition of multiple additives, thus avoiding disadvantages such as high viscosity and high cost.

[0022] Preferably, the additive accounts for 1 to 5% of the mass percentage of the magnesium battery electrolyte.

[0023] The present invention also provides a method for preparing the magnesium battery electrolyte as described herein, comprising the following steps:

[0024] Moisture was removed from magnesium salt electrolytes, organoboronic acids and their derivatives, organic ether solvents and additives, respectively.

[0025] Under anhydrous and oxygen-free conditions, magnesium salt electrolyte and organic ether solvent are mixed, and then organic boric acid and its derivatives and additives are added sequentially under stirring. The mixture is stirred for 8 to 30 hours to obtain magnesium battery electrolyte.

[0026] Preferably, 3A molecular sieve activated at 300°C for 5 hours is used to remove moisture from the organoboronic acid and its derivatives, organic ether solvents and liquid additives, and vacuum drying is used to remove moisture from the magnesium salt electrolyte and immobilized additives. The vacuum drying conditions are vacuum drying at 80-120°C for 24-72 hours.

[0027] The present invention also provides a magnesium battery, wherein the electrolyte in the magnesium battery is the magnesium battery electrolyte described in the present invention.

[0028] The beneficial effects of this invention are:

[0029] The magnesium battery electrolyte of this invention improves the solubility of magnesium salts by using a non-nucleophilic electrolyte as the magnesium salt and an organic ether solvent as the organic solvent. This type of magnesium salt exhibits a suitable binding affinity with the organic ether solvent. Furthermore, by adding organic boric acid and its derivatives to the magnesium battery electrolyte, it readily binds with electron-rich substances (such as F...). - The combination of materials enhances the Mg 2+ The dissociation of ions with anions effectively improves ionic conductivity and reduces interfacial impedance, thereby accelerating the battery's kinetic process. Using HFE as an additive, its -CF3 content has a strong electron-withdrawing ability, thus suppressing electron loss under high voltage. It also readily combines with electron-deficient organic boric acids and their derivatives, thereby improving anodic oxidation stability. By avoiding the introduction of chlorine-containing compounds into the magnesium battery electrolyte, it is non-corrosive to the current collector and battery casing, thus significantly extending the battery's operating life.

[0030] The preparation method of the magnesium battery electrolyte of the present invention is simple and has a short synthesis time, and the reaction conditions are mild. At the same time, no toxic gases are generated during the reaction process, which meets the requirements of green environmental protection. Therefore, it is easy to use for large-scale industrial production and has promotion and application value in the field of magnesium-ion battery technology. Attached Figure Description

[0031] Figure 1 The cyclic voltammetry curve of the magnesium battery electrolyte prepared in Example 6 of this invention on SS;

[0032] Figure 2 Linear sweep voltammetry curves of the magnesium battery electrolyte prepared in Example 6 of this invention on different current collectors;

[0033] Figure 3 The magnesium battery electrolyte prepared in Example 6 of this invention uses stainless steel SS as the working electrode at 0.1 mA / cm². 2 Cyclic curves and coulombic efficiency of reversible magnesium deposition / dissolution at current density;

[0034] Figure 4The Mg / / Mg symmetric cell assembled with the magnesium battery electrolyte prepared in Example 6 of this invention operates at 0.1 mA / cm². 2 Long-cycle polarization curves at current density;

[0035] Figure 5 Rate polarization curves of Mg / / Mg symmetric cells assembled with the magnesium battery electrolyte prepared in Example 6 of this invention at different current densities. Detailed Implementation

[0036] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0037] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of this application; however, it will be apparent to those skilled in the art that embodiments of this application may be implemented without these specific details.

[0039] Example 1

[0040] A magnesium battery electrolyte comprising 3.188 g of 0.25 mol L⁻¹ -1 Bis(diisopropylamino)magnesium (MBA), 3.278 g 0.125 mol L -1 (Dimethylbenzylsilane-based) pinacol ester (DPFB), 1.75 g 50 mol L -1 The mixture contained decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) and 100 mL of tetrahydrofuran (THF).

[0041] Example 2

[0042] A magnesium battery electrolyte comprising 16.122 g of 0.5 mol / L... -1 Magnesium trifluoromethanesulfonate, 3.48 g 0.125 mol L -1Tris(trimethylsilane)boronic acid ester, 0.700 g 50 mol L -1 The decafluoro-3-methoxy-2-trifluoromethylpentane and 100 mL of ethylene glycol dimethyl ether.

[0043] Example 3

[0044] A magnesium battery electrolyte comprising 4.603 g of 0.25 mol / L... -1 Magnesium bromide, 1.639 g 0.125 mol L -1 (Dimethylbenzyl)boronic acid pinacol ester, 0.178 g 50 mol L -1 Tetramethylammonium borohydride and 100 mL tetraethylene glycol dimethyl ether.

[0045] Example 4

[0046] A magnesium battery electrolyte comprising 3.463 g of 0.25 mol / L... -1 di-n-butylmagnesium, 2.978 g 0.125 mol L -1 0.257 g 50 mol L of β-methoxy-10-trimethylsilyl-9-boronbicyclo(3.3.2)decane -1 Tetrabutylborohydride and 50 mL tetrahydrofuran + 50 mL ethylene glycol dimethyl ether.

[0047] Example 5

[0048] A magnesium battery electrolyte comprising 0.540 g of 0.1 mol L⁻¹ -1 Magnesium borohydride + 23.380g 0.4mol L -1 Magnesium bis(trifluoromethanesulfonyl)imide, 1.639 g 0.125 mol L -1 (Dimethylbenzyl)borate pinacol ester, 1.041 g 50 mol L -1 2,2-Dimethoxypropane and 100 mL of tetrahydrofuran.

[0049] Example 6

[0050] A method for preparing a magnesium battery electrolyte as described in Example 1 includes the following steps:

[0051] S1. Pretreatment of bis(diisopropylamino)magnesium (MBA): At a temperature of 80-120℃, MBA is vacuum dried for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0052] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to tetrahydrofuran (THF) while hot, and store in a glove box in a sealed container.

[0053] S3, Pretreatment of (dimethylbenzyl)borate pinacol ester (DPFB) / decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the volatilization of the reagent, it was added to DPFB and HFE respectively after the molecular sieve was cooled to room temperature to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0054] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 3.188 g of MBA (0.25 mol / L) was taken. -1 The solution was slowly added to 100 mL of tetrahydrofuran (THF) under stirring and stirred for 24 h; subsequently, 3.278 g of DPFB (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 24 hours to obtain the basic electrolyte (DPFB / MBA = 1:2); finally, 1.75 g of HFE (50 mol L) was added under stirring. -1 Additives were added and stirred for 24 hours to obtain magnesium battery electrolyte.

[0055] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0056] Example 7

[0057] A method for preparing a magnesium battery electrolyte as shown in Example 2 includes the following steps:

[0058] S1. Pretreatment of magnesium trifluoromethanesulfonate: At a temperature of 80-120℃, magnesium trifluoromethanesulfonate is vacuum dried for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0059] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to ethylene glycol dimethyl ether while hot, and store in a glove box in a sealed container.

[0060] S3, Pretreatment of tris(trimethylsilane)borate / decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the volatilization of the reagent, the molecular sieve was cooled to room temperature before being added to tris(trimethylsilane)borate and HFE respectively to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0061] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 16.122 g of magnesium trifluoromethanesulfonate (0.5 mol / L) was taken. -1The solution was slowly added to 100 mL of ethylene glycol dimethyl ether under stirring and stirred for 30 h; subsequently, 3.48 g of tris(trimethylsilane)borate (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 24 hours to obtain the basic electrolyte; finally, 0.7 g of HFE (50 mol / L) was added under stirring. -1 Additives were added and stirred for 12 hours to obtain magnesium battery electrolyte.

[0062] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0063] Example 8

[0064] A method for preparing a magnesium battery electrolyte as shown in Example 3 includes the following steps:

[0065] S1. Pretreatment of magnesium bromide: At a temperature of 80-120℃, magnesium bromide is vacuum dried for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0066] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to tetraethylene glycol dimethyl ether while hot, and store in a glove box in a sealed container.

[0067] S3, Pretreatment of (dimethylbenzyl)borate pinacol ester (DPFB) / tetramethylborohydride reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the reagent from volatilizing, the molecular sieve was cooled to room temperature before being added to DPFB and tetramethylborohydride respectively to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0068] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 4.603 g of magnesium bromide (0.25 mol / L) was taken. -1 The solution was slowly added to 100 mL of tetraethylene glycol dimethyl ether under stirring, and stirred for 12 h; subsequently, 1.639 g of DPFB (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 24 hours to obtain the basic electrolyte; finally, 0.178 g of tetramethylammonium borohydride (50 mol / L) was added under stirring. -1 Additives were added and stirred for 8 hours to obtain magnesium battery electrolyte.

[0069] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0070] Example 9

[0071] A method for preparing a magnesium battery electrolyte as shown in Example 4 includes the following steps:

[0072] S1. Pretreatment of di-n-butylmagnesium: Di-n-butylmagnesium is vacuum dried at a temperature of 80-120℃ for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0073] S2. Pretreatment of organic ether solvents: Add 3A molecular sieve activated at 300℃ for 5h to tetrahydrofuran (THF) and ethylene glycol dimethyl ether while hot, and store in a glove box in a sealed container.

[0074] Pretreatment of S3, B-methoxy-10-trimethylsilyl-9-boronbicyclo(3.3.2)decane / tetrabutylborohydride reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the volatilization of the reagent, after the molecular sieve was cooled to room temperature, it was added to B-methoxy-10-trimethylsilyl-9-boronbicyclo(3.3.2)decane and tetrabutylborohydride respectively to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0075] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 3.463 g of di-n-butylmagnesium (0.25 mol / L) was taken. -1 Under stirring, the solution was slowly added to a mixed ether solvent of 50 mL tetrahydrofuran and 50 mL ethylene glycol dimethyl ether, and stirred for 18 h. Subsequently, 2.978 g of 0.125 mol / L β-methoxy-10-trimethylsilyl-9-boron bicyclo(3.3.2)decane was added under stirring. -1 The mixture was stirred for 20 hours to obtain the basic electrolyte; finally, 0.257 g of tetrabutylammonium borohydride (50 mol / L) was added under stirring. -1 Additives were added and stirred for 14 hours to obtain magnesium battery electrolyte.

[0076] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0077] Example 10

[0078] A method for preparing a magnesium battery electrolyte as shown in Example 5 includes the following steps:

[0079] S1. Pretreatment of magnesium borohydride / bis(trifluoromethanesulfonyl)imide magnesium: At a temperature of 80-120℃, magnesium borohydride / bis(trifluoromethanesulfonyl)imide magnesium is vacuum dried for 24-72h to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0080] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to tetrahydrofuran (THF) while hot, and store in a glove box in a sealed container.

[0081] S3, (Dimethylbenzylsilane-based)Pinacol ester borate (DPFB) / 2,2-dimethoxypropane reagent pretreatment: 3A molecular sieve was dried at 300℃ for 5h. To prevent the reagent from volatilizing, the molecular sieve was cooled to room temperature before being added to DPFB and 2,2-dimethoxypropane respectively to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0082] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 0.540 g of magnesium borohydride (0.1 mol / L) was used. -1 ) + 23.380g bis(trifluoromethanesulfonyl)imide magnesium (0.4mol L) -1 The solution was slowly added to 100 mL of tetrahydrofuran (THF) under stirring and stirred for 24 h; subsequently, 1.639 g of DPFB (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 18 hours to obtain the basic electrolyte; finally, 1.041 g of 2,2-dimethoxypropane (50 mol / L) was added under stirring. -1 Additives were added and stirred for 10 hours to obtain magnesium battery electrolyte.

[0083] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0084] Comparative Example 1

[0085] A method for preparing a magnesium battery electrolyte includes the following steps:

[0086] S1. Pretreatment of bis(diisopropylamino)magnesium (MBA): At a temperature of 80-120℃, MBA is vacuum dried for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0087] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to tetrahydrofuran (THF) while hot, and store in a glove box in a sealed container.

[0088] S3, Pretreatment of (dimethylbenzyl)borate pinacol ester (DPFB) reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the reagent from volatilizing, the molecular sieve was cooled to room temperature before being added to DPFB to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0089] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. Take 5.205 g of MBA (0.25 mol / L) -1The solution was slowly added to 100 mL of tetrahydrofuran (THF) under stirring and stirred for 24 h; subsequently, 3.28 g of DPFB (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 24 hours to obtain a magnesium battery electrolyte (DPFB / MBA = 1:2).

[0090] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0091] Comparative Example 2

[0092] A method for preparing a magnesium battery electrolyte includes the following steps:

[0093] S1. Pretreatment of bis(diisopropylamino)magnesium (MBA): At a temperature of 80-120℃, MBA is vacuum dried for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0094] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to tetrahydrofuran (THF) while hot, and store in a glove box in a sealed container.

[0095] S3, Pretreatment of (dimethylbenzyl)borate pinacol ester (DPFB) reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the reagent from volatilizing, the molecular sieve was cooled to room temperature before being added to DPFB to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0096] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 3.188 g of MBA (0.25 mol / L) was taken. -1 The solution was slowly added to 100 mL of tetrahydrofuran (THF) under stirring and stirred for 24 h; subsequently, 3.500 g of DPFB (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 24 hours to obtain a magnesium battery electrolyte (DPFB / MBA = 1:1).

[0097] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0098] Comparative Example 3

[0099] A method for preparing a magnesium battery electrolyte includes the following steps:

[0100] S1. Pretreatment of bis(diisopropylamino)magnesium (MBA): At a temperature of 80-120℃, MBA is vacuum dried for 24-72 hours to remove trace amounts of moisture, and then sealed and placed in an anhydrous and oxygen-free glove box.

[0101] S2. Pretreatment of organic ether solvent: Add 3A molecular sieve activated at 300℃ for 5h to tetrahydrofuran (THF) while hot, and store in a glove box in a sealed container.

[0102] S3, Pretreatment of (dimethylbenzyl)borate pinacol ester (DPFB) reagent: 3A molecular sieve was dried at 300℃ for 5h. To prevent the reagent from volatilizing, the molecular sieve was cooled to room temperature before being added to DPFB to remove trace amounts of moisture. After sealing, it was placed in an anhydrous and oxygen-free glove box.

[0103] S4. Electrolyte preparation: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. 3.188 g of MBA (0.25 mol / L) was taken. -1 The solution was slowly added to 100 mL of tetrahydrofuran (THF) under stirring and stirred for 24 h; subsequently, 7.000 g of DPFB (0.125 mol / L) was added under stirring. -1 The mixture was stirred for 24 hours to obtain a magnesium battery electrolyte (DPFB / MBA = 2:1).

[0104] All of the above reactions were carried out in a dry glove box with a water / oxygen content of less than 0.01 ppm.

[0105] Electrochemical performance testing and analysis

[0106] 1) Magnesium reversible deposition / dissolution and oxidation stability test

[0107] The reversible deposition / dissolution coulombic efficiency and oxidation stability of magnesium in the magnesium battery electrolyte were tested using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), respectively, with a Shanghai Chenhua CHI 660 electrochemical workstation. Tests were conducted using assembled CR2032 coin cells, with stainless steel (SS) as the positive electrode current collector, polished magnesium sheets as the negative electrode, and a GF / A glass fiber membrane as the separator. The assembled cells were allowed to stand at room temperature for at least 4 hours before testing. The CV scan rate was 25 mV / s, with a voltage range of -0.8 V to 2.0 V; the LSV scan range was from open circuit voltage to 4.5 V, with a scan rate of 5 mV / s.

[0108] Cyclic voltammetry tests were performed on the magnesium battery electrolyte prepared in Example 6 using stainless steel SS, molybdenum foil, or copper foil as the working electrode. The cyclic voltammetry curves are shown below. Figure 1 As shown, from Figure 1 Analysis shows that the electrochemical stability potential (vs. Mg / Mg) of the magnesium battery electrolyte prepared in Example 6 on stainless steel, molybdenum foil, and copper foil is [not specified]. 2+The values ​​were all relatively high, at 3.2V, 3.1V and 2.8V respectively, which proves that the anodic stability of the magnesium battery electrolyte is good.

[0109] Using stainless steel SS as the working electrode, a linear sweep voltammetry test was performed on the magnesium battery electrolyte prepared in Example 6. The linear sweep voltammetry curve is shown below. Figure 2 As shown, from Figure 2 Analysis shows that the deposition overpotential of the magnesium battery electrolyte prepared in Example 6 is -210mV and the dissolution overpotential is 200mV, thus proving that the magnesium battery electrolyte can undergo reversible deposition / dissolution.

[0110] 2) Coulombic efficiency test of magnesium reversible deposition / dissolution performance

[0111] The reversible deposition / dissolution performance and coulombic efficiency of the magnesium battery electrolyte were tested using a constant current charge-discharge (CP) tester from Wuhan Landian. Testing was conducted using assembled CR2032 coin cells. The positive electrode current collector was made of stainless steel (SS), the negative electrode was a polished magnesium sheet, and the separator was a GF / A glass fiber membrane. The assembled cells were allowed to stand at room temperature for at least 4 hours before testing. The CP test had a discharge time of 30 minutes, a charging cutoff voltage of 2V, and a current density of 0.1 mA / cm². 2 .

[0112] Using stainless steel SS as the working electrode, the coulombic efficiency of the magnesium battery electrolyte prepared in Example 6 was tested, such as... Figure 3 As shown, from Figure 3 Analysis shows that the magnesium battery electrolyte prepared in Example 6 has a performance of 0.1 mA / cm². 2 The average deposition / dissolution efficiency reached 99.5% after 200 cycles at a current density, demonstrating that the magnesium battery electrolyte has high coulombic efficiency and good cycle performance.

[0113] 3) Polarization performance test

[0114] The polarization performance of the magnesium battery electrolyte was tested by constant current charge-discharge (CP) using the Wuhan Landian charge-discharge tester.

[0115] Specifically, the magnesium battery electrolyte prepared in Example 6 was tested by assembling a CR2032 coin-type Mg / / Mg symmetric battery. Both the positive and negative electrodes were made of polished magnesium sheets (Mg), and the separator was a GF / A glass fiber membrane. The assembled battery was allowed to stand at room temperature for at least 4 hours before testing. The charge-discharge test (CP) had a discharge time of 30 minutes and a charging time of 30 minutes, with a current of 0.05 mA / cm². 2 ~2mA / cm 2 .

[0116] The Mg / / Mg symmetric cell assembled with the magnesium battery electrolyte prepared in Example 6 operates at 0.1 mA / cm². 2 Long-cycle polarization curves at current density are as follows Figure 4 As shown.

[0117] from Figure 4 Analysis shows that the magnesium battery electrolyte prepared in Example 6 has a performance of 0.1 mA / cm². 2 At a current density of 180 mV, the initial polarization potential is as low as 180 mV. After 800 cycles, the polarization potential increases to 210 mV, and the overpotential does not increase significantly, thus proving that the electrolyte of this magnesium battery has low polarization and excellent cycle performance.

[0118] The rate polarization curves of the Mg / / Mg symmetric cells assembled with the magnesium battery electrolyte prepared in Example 6 at different current densities are shown below. Figure 5 As shown.

[0119] from Figure 5 Analysis shows that when the current density increases from 0.05 mA / cm², the... 2 Gradually increase to 2mA / cm 2 At that time, the polarization potential of the magnesium battery electrolyte prepared in Example 6 increased from 230mV to no more than about 400mV, thus proving that the magnesium battery electrolyte can withstand a large current density.

[0120] The electrochemical performance of the magnesium battery electrolytes prepared in Examples 7-10 and Comparative Examples 1-3 was tested using the same testing methods described above, and the results are shown in Table 1.

[0121] Table 1 Electrochemical performance test results of magnesium battery electrolyte

[0122] Electrochemical window (SS) / V Deposition / Dissolution Efficiency (SS) / % Overpotential / mV Example 7 3.3 99.2 170 Example 8 3.2 98.7 200 Example 9 3.0 98.3 180 Example 10 3.2 98.1 220 Comparative Example 1 2.3 99.1 280 Comparative Example 2 2.2 98.2 320 Comparative Example 3 2.0 97.5 350

[0123] As can be seen from the comprehensive analysis in Table 1, the magnesium battery electrolyte of the present invention has significant advantages such as a high electrochemical window, high deposition / dissolution coulombic efficiency, and long cycle life.

[0124] In summary, the magnesium battery electrolyte of this invention addresses the problems of existing magnesium-ion battery electrolytes, which are mostly corrosive due to chlorine content and have a low voltage window. By adjusting the ratio of magnesium salt to organic boric acid and its derivatives, and by introducing fluorine-containing additives or dehydrating additives, an electrolyte with high anodic stability is achieved. The magnesium battery of this invention has a wide electrochemical window, high deposition / dissolution efficiency, low overpotential, and advantages such as simple preparation and low cost. Most importantly, this magnesium battery electrolyte does not contain corrosive ions and will not corrode the current collector or battery casing, thus contributing to extended battery life. In conclusion, this magnesium-ion electrolyte has excellent commercial prospects and is valuable for widespread application in the field of magnesium-ion battery technology.

[0125] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A magnesium battery electrolyte, characterized in that, The electrolyte comprises magnesium salt electrolyte, organic boric acid and its derivatives, organic ether solvent and additives, wherein the magnesium battery electrolyte does not contain chlorine-containing compound additives, and the magnesium salt electrolyte is a non-nucleophilic electrolyte. The molar ratio of the magnesium salt electrolyte to the organoboronic acid and its derivatives is 1:0.5~5, and the organoboronic acid and its derivatives are one or more of (dimethylbenzylsilane)boronic acid pinacol ester, tris(trimethylsilane)boronic acid ester, and β-methoxy-10-trimethylsilyl-9-boronbicyclo(3.3.2)decane; The additive is decafluoro-3-methoxy-2-trifluoromethylpentane, 2,2-dimethoxypropane, or a quaternary ammonium salt of borohydride.

2. The magnesium battery electrolyte according to claim 1, characterized in that, The magnesium salt electrolyte is one or more of bis(diisopropylamino)magnesium, magnesium borohydride, n-butylmagnesium, bis(trifluoromethanesulfonyl)imide magnesium (Mg(TFSI)2), and magnesium trifluoromethanesulfonate.

3. The magnesium battery electrolyte according to claim 1, characterized in that, The organic ether solvent is one or more selected from tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; The borohydride quaternary ammonium salt includes one or more of tetramethylammonium borohydride, tetraethylammonium borohydride, and tetrabutylammonium borohydride.

4. The magnesium battery electrolyte according to claim 1, characterized in that, The magnesium salt electrolyte is bis(diisopropylamino)magnesium; the organoboronic acid and its derivatives are (dimethylbenzylsilane)boronic acid pinacol ester; the additive is decafluoro-3-methoxy-2-trifluoromethylpentane.

5. The magnesium battery electrolyte according to claim 1, characterized in that, The additive accounts for 1-5% of the mass percentage of the magnesium battery electrolyte.

6. A method for preparing a magnesium battery electrolyte as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Moisture was removed from magnesium salt electrolytes, organoboronic acids and their derivatives, organic ether solvents and additives, respectively. Under anhydrous and oxygen-free conditions, magnesium salt electrolyte and organic ether solvent are mixed, and then organic boric acid and its derivatives and additives are added sequentially under stirring. The mixture is stirred for 8 to 30 hours to obtain magnesium battery electrolyte.

7. The method for preparing the magnesium battery electrolyte according to claim 6, characterized in that, Moisture in the organoboronic acid and its derivatives, organic ether solvents and liquid additives is removed by using 3A molecular sieve activated at 300℃ for 5 hours. Moisture in the magnesium salt electrolyte and immobilized additives is removed by vacuum drying at 80~120℃ for 24~72 hours.

8. A magnesium battery, characterized in that, The electrolyte in the magnesium battery is the magnesium battery electrolyte according to any one of claims 1 to 5.

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