CN115954549A - Magnesium battery electrolyte, preparation method and magnesium battery - Google Patents
Magnesium battery electrolyte, preparation method and magnesium battery Download PDFInfo
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Abstract
The invention relates to a magnesium battery electrolyte, a preparation method and a magnesium battery. The magnesium battery electrolyte comprises a magnesium salt electrolyte, organic boric acid and derivatives thereof, an organic ether solvent and an additive, wherein the magnesium battery electrolyte does not contain a chlorine-containing compound, the magnesium salt electrolyte is a non-nucleophilic electrolyte, and the additive is a water-removing additive. The invention also provides a preparation method of the magnesium battery electrolyte, which is used for respectively removing moisture in magnesium salt electrolyte, organic boric acid and derivatives thereof, organic ether solvent and additives; mixing a magnesium salt electrolyte with an organic ether solvent under the anhydrous and anaerobic conditions, sequentially adding organic boric acid and derivatives thereof and an additive under the stirring condition, and stirring for 8 to 30h to obtain the magnesium battery electrolyte. The invention also provides a magnesium battery, and the electrolyte in the magnesium battery is the magnesium battery electrolyte. The invention solves the problems of narrow electrochemical window, short cycle life and the like of the magnesium battery.
Description
Technical Field
The invention relates to the technical field of magnesium batteries, in particular to a magnesium battery electrolyte, a preparation method and a magnesium battery.
Background
Nowadays, portable electronic products and electric vehicles put higher demands on energy storage batteries. In recent years, magnesium ion batteries have high volumetric specific energy (3832 mAh/cm) 3 ) Negative redox potential (-2.37v vs. she), high earth crust abundance, good safety, etc., and thus the rechargeable magnesium battery becomes an excellent candidate for next-generation energy storage. However, successful commercialization of rechargeable magnesium batteries faces severe passivation of the magnesium negative electrode, slow kinetics of the positive electrode, and very low battery power densities (< 0.5kW kg) -1 ,0.8mW cm -2 ) To (3) is described.
The electrolyte serves as the 'blood' of the battery and plays a crucial role in the overall performance of the battery. In magnesium ion batteries, interfacial layers caused by electrolyte decomposition often block Mg 2+ Diffusion of (2). Therefore, most simple ionic salts (e.g., mg (ClO)) that readily form passivation films 4 ) 2 And Mg (BF) 4 ) 2 ) And polar aprotic solvents (such as carbonates and nitriles) are not suitable as electrolytes for magnesium ion batteries.
In the existing magnesium ion battery electrolyte technology, a nucleophilic electrolyte can be compatible with a Mg intercalation anode, but Mg is compatible at room temperature 2+ Is subjected to Mg at the electrode/electrolyte interface 2+ The high energy barrier to desolvation and its low diffusion rate in the material. In addition, nucleophilic components are susceptible to chemical reactions with electrophilic materials and are not suitable for organic polymer electrodes and switching anodes (e.g., sulfur, iodine). Researchers have now conducted extensive research on non-nucleophilic electrolytes, with bis (diisopropylamino) Magnesium (MBA) as a common electrolyte component due to its high coulombic efficiencyAnd low overpotential are of particular interest.
MBA as a cheap non-nucleophilic electrolyte ($ 66/0.7 mol L) -1 (100 mL THF), reduced to $ 4.2/g), is a promising magnesium salt to replace the current expensive and difficult to prepare magnesium salts, such as Mg (TFSI) 2 ,Mg(HMDS) 2 And Mg (B (hfip) 4 ) 2 And a holophenyl complex (APC). However, MBA/THF electrolytes have limited ionic conductivity and a poor electrochemical window, and in most of the prior art, mgCl needs to be introduced 2 Or AlCl 3 To improve. For example, CN113258138A discloses a full inorganic salt type rechargeable magnesium battery electrolyte and a preparation method thereof, wherein MgCl is added into the electrolyte 2 And containing Cl - Co-solvents and activators. Therefore, lewis acid (AlCl) containing Al is introduced 3 、AlEtCl 2 And Me 2 AlCl) has been widely used to improve the compatibility of the negative electrode-electrolyte interface and broaden the stability of the anode. Appropriate amount of Cl - Is thought to contribute not only to the stabilization of Mg 2+ But also helps to dissolve the passivation species on the Mg anode, thereby hindering the formation of an anode passivation film and realizing reversible Mg plating/demagging. More recently, 1-ethyl-3-methylimidazolium tetrachloroaluminate [ C 2 mim][AlCl 4 ]Was first introduced into MBA-based electrolytes and demonstrated to support reversible Mg deposition/dissolution with a coulombic efficiency of 92% on Stainless Steel (SS). However, cl in the electrolyte - This results in a reduction in the efficiency of the magnesium deposition cycle. Most critical is the Cl in the anionic component - Elements and their associated ligand compounds can cause severe corrosion of common current collectors such as SS, al and Cu. Meanwhile, the electrolyte inevitably contains trace moisture and impurities, namely H 2 In the presence of O, free Cl - Attack the negative metal Mg and reduce the deposition/dissolution coulombic efficiency. Thus, cl - The presence of (a) has an extremely adverse effect on the long-term cycling of the battery, and eventually the battery is liable to fail.
In summary, in the prior art MBA non-nucleophilic electrolyte, cl - Introduction can lead to narrow electrochemical window and short cycle lifeTo give a title. Therefore, there is a need to develop an MBA-based electrolyte with simple preparation, low cost and wide electrochemical window to promote the development and commercial application of electrolyte for rechargeable magnesium ion batteries.
Disclosure of Invention
The invention aims to provide a magnesium battery electrolyte, a preparation method and a magnesium battery, and aims to solve the problems of narrow electrochemical window, short cycle life and the like of the magnesium battery.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the magnesium battery electrolyte comprises a magnesium salt electrolyte, organic boric acid and derivatives thereof, an organic ether solvent and an additive, wherein the magnesium battery electrolyte does not contain a chlorine-containing compound additive, the magnesium salt electrolyte is a non-nucleophilic electrolyte, and the additive is a water-removing additive.
According to the technical means, the non-nucleophilic electrolyte is used as the magnesium salt in the electrolyte of the magnesium battery, and the organic ether solvent is used as the organic solvent, so that the magnesium salt and the organic ether solvent have moderate binding capacity, and the solubility of the magnesium salt is improved; by adding organic boric acid and its derivatives into magnesium battery electrolyte, it is easy to react with rich electrons (such as F) - ) Material bonding, enhanced Mg 2+ The ionic pair dissociation with anions effectively improves the ionic conductivity and reduces the interface impedance, thereby accelerating the dynamic process of the battery; using HFE as additive, which contains-CF 3 The organic boric acid has strong electron-withdrawing capability, so that the electron loss under high voltage is inhibited, and the organic boric acid and the derivative thereof are easy to combine with electron-deficient bodies, so that the anodic oxidation stability is improved; the magnesium battery electrolyte is not introduced with a chlorine-containing compound, so that the magnesium battery electrolyte has no corrosivity on a current collector and a battery shell, and the service life of the battery can be greatly prolonged.
Preferably, the magnesium salt electrolyte is bis (diisopropylamino) Magnesium (MBA), magnesium borohydride, n-butyl magnesium, bis (trifluoromethanesulfonyl) imide magnesium (Mg (TFSI) 2 ) And magnesium triflate.
Preferably, the magnesium salt electrolyte is bis (diisopropylamino) Magnesium (MBA).
Preferably, the organic boric acid and the derivative thereof are one or more of (dimethyl phenyl silyl) boric acid pinacol ester (DPFB), tri (trimethyl silane) borate and B-methoxy-10-trimethylsilyl-9-borabicyclo (3.3.2) decane.
Preferably, the organic ether solvent is one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether;
the additive is decafluoro-3-methoxy-2-trifluoromethyl pentane (HFE), 2-dimethoxypropane or quaternary ammonium borohydride salt;
the quaternary ammonium borohydride salt comprises one or more of tetramethylammonium borohydride, tetraethylammonium borohydride and tetrabutylammonium borohydride.
Preferably, the magnesium salt electrolyte is bis (diisopropylamino) Magnesium (MBA); the organic boric acid and the derivative thereof are (dimethyl phenyl silyl) boric acid pinacol ester (DPFB); the additive is decafluoro-3-methoxy-2-trifluoromethylpentane (HFE).
Among them, the electrolyte of magnesium salt is preferably MBA, and the magnesium salt has moderate binding capacity with ether solvents, so that the magnesium salt is easy to dissolve in the ether solvents such as THF and the like. The electrolyte has rich raw materials and low price, and is easy for mass production.
DPTB in magnesium battery electrolyte is an electron-deficient boron compound and an anion acceptor, can prevent the decomposition of anions in the electrolyte and is easy to react with rich electrons (such as F) - ) Material bonding, reinforcing Mg 2+ And ion pairs with anions are dissociated, so that the ionic conductivity is improved, and the interface impedance is reduced, thereby accelerating the dynamic process of the battery. Among the decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) additives used, -CF 3 The fluorine has strong electron-withdrawing ability, and the strong attraction of fluorine to electrons can inhibit electron loss under high voltage, and is easy to combine with DPTB electron-deficient bodies, thereby improving the anodic oxidation stability. In addition, DPTB can also form a thinner positive electrode-electrolyte interface, which favors Mg 2+ Inhibit rapid degradation of the capacity of the positive electrode material.
Preferably, the molar ratio of the magnesium salt electrolyte to the organic boric acid and the derivative thereof is 1.
The high-voltage circulation of the magnesium battery electrolyte can be realized by reasonably adjusting the molar ratio of DPTB to MBA in the magnesium battery electrolyte, and expensive additives such as B-based components or ionic liquid are not needed to be used, and various additives are not needed to be added, so that the disadvantages of high viscosity, high cost and the like are avoided.
Preferably, the additive accounts for 1-5% of the magnesium battery electrolyte by mass.
The invention also provides a preparation method of the magnesium battery electrolyte, which comprises the following steps:
respectively removing moisture in magnesium salt electrolyte, organic boric acid and derivatives thereof, organic ether solvent and additives;
under the anhydrous and anaerobic conditions, mixing a magnesium salt electrolyte with an organic ether solvent, sequentially adding organic boric acid and derivatives thereof and an additive under the stirring condition, and stirring for 8-30 h to obtain the magnesium battery electrolyte.
Preferably, the 3A molecular sieve activated at 300 ℃ for 5 hours is used for removing the moisture in the organic boric acid and the derivatives thereof, the organic ether solvent and the liquid additive, the vacuum drying is used for removing the moisture in the magnesium salt electrolyte and the fixed additive, and the vacuum drying condition is that the vacuum drying is carried out at 80-120 ℃ for 24-72 hours.
The invention also provides a magnesium battery, and the electrolyte in the magnesium battery is the magnesium battery electrolyte.
The invention has the beneficial effects that:
according to the magnesium battery electrolyte, the non-nucleophilic electrolyte is used as the magnesium salt in the magnesium battery electrolyte, and the organic ether solvent is used as the organic solvent, so that the magnesium salt and the organic ether solvent have moderate binding capacity, and the solubility of the magnesium salt is improved; by adding organic boric acid and its derivatives into magnesium battery electrolyte, it is easy to react with rich electrons (such as F) - ) Material bonding, enhanced Mg 2+ Ion pair dissociation with anion effectively improves ion conductivity and reducesThe interface impedance is low, so that the dynamic process of the battery is accelerated; using HFE as additive, which contains-CF 3 The organic boric acid has strong electron-withdrawing capability, so that the electron loss under high voltage is inhibited, and the organic boric acid and the derivative thereof are easy to combine with electron-deficient bodies, so that the anodic oxidation stability is improved; the magnesium battery electrolyte is not introduced with a chlorine-containing compound, so that the magnesium battery electrolyte has no corrosivity on a current collector and a battery shell, and the service life of the battery can be greatly prolonged;
the preparation method of the magnesium battery electrolyte is simple, short in synthesis time and mild in reaction conditions; meanwhile, no toxic gas is generated in the reaction process, and the method meets the requirement of environmental protection, so the method is easy to be used for large-scale industrial production, and has popularization and application values in the technical field of magnesium ion batteries.
Drawings
FIG. 1 is a cyclic voltammogram of a magnesium battery electrolyte prepared in example 6 of the present invention on SS;
fig. 2 is a linear sweep voltammetry curve of the electrolyte of the magnesium battery prepared in example 6 of the present invention on different current collectors;
FIG. 3 shows that the electrolyte for magnesium battery prepared in example 6 of the present invention is applied at 0.1mA/cm using stainless steel SS as the working electrode 2 The cycle curve of reversible magnesium deposition/dissolution at current density and coulombic efficiency;
FIG. 4 shows that the electrolyte of the magnesium cell prepared in example 6 of the present invention is used to assemble a symmetrical Mg// Mg cell at 0.1mA/cm 2 A long circular polarization curve at current density;
FIG. 5 is a graph showing the rate polarization curves of Mg// Mg symmetrical cells assembled with the electrolyte of the magnesium cell prepared in example 6 of the present invention at different current densities.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure herein, wherein the embodiments of the present invention are described in detail with reference to the accompanying drawings and preferred embodiments. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be understood that the preferred embodiments are illustrative of the invention only and are not limiting upon the scope of the invention.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
In the following description, numerous details are set forth to provide a more thorough explanation of the embodiments of the present application, however, it will be apparent to one skilled in the art that the embodiments of the present application may be practiced without these specific details.
Example 1
A magnesium battery electrolyte comprises 3.188g0.25mol L -1 Bis (diisopropylamino) Magnesium (MBA), 3.278g0.125mol L -1 (Dimethylbenzosilyl) boronic acid pinacol ester (DPFB), 1.75g50mol L -1 Decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) and 100mL Tetrahydrofuran (THF).
Example 2
The electrolyte of the magnesium battery comprises 16.122g of 0.5mol L -1 Of magnesium trifluoromethanesulfonate, 3.48g0.125mol L -1 Tris (trimethylsilyl) borate, 0.700g50mol L -1 Decafluoro-3-methoxy-2-trifluoromethylpentane and 100mL of ethylene glycol dimethyl ether.
Example 3
A magnesium battery electrolyte comprises 4.603g 0.25mol L -1 Magnesium bromide, 1.639g0.125mol L -1 (Dimethylbenzsilyl) boronic acid pinacol ester of (9), 0.178g50mol L -1 Tetramethylammonium borohydride and 100mL tetraethylene glycol dimethyl ether.
Example 4
A magnesium battery electrolyte comprises 3.463g0.25mol L -1 Di-n-butylmagnesium of (2.978g0.125mol L) -1 B-methoxy of (2)Alkyl-10-trimethylsilyl-9-borabicyclo (3.3.2) decane, 0.257g50mol L -1 Tetrabutylammonium borohydride and 50mL tetrahydrofuran +50mL ethylene glycol dimethyl ether.
Example 5
A magnesium battery electrolyte comprises 0.540g 0.1mol L -1 23.380g of magnesium borohydride and 0.4mol L of magnesium borohydride -1 Magnesium bis (trifluoromethanesulfonyl) imide(s) 1.639g0.125mol L -1 (Dimethylbenzylsilyl) boronic acid pinacol ester of (1.041g 50mol L) -1 2, 2-dimethoxypropane and 100mL of tetrahydrofuran.
Example 6
A method of preparing the electrolyte for a magnesium battery as in example 1, comprising the steps of:
s1, pretreatment of bis (diisopropylamino) Magnesium (MBA): drying MBA for 24-72 h in vacuum at 80-120 ℃ to remove trace moisture, sealing, and standing in an anhydrous and oxygen-free glove box;
s2, pretreatment of an organic ether solvent: adding 3A molecular sieve activated at 300 deg.C for 5 hr in Tetrahydrofuran (THF), and storing in glove box;
pretreatment of S3, (dimethylsilyl) boronic acid pinacol ester (DPFB)/decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) reagent: drying 3A molecular sieve at 300 deg.C for 5 hr, cooling to room temperature, adding into DPFB and HFE to remove trace water, sealing, and standing in anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, and 3.188g of MBA (0.25 mol L) were taken -1 ) Slowly adding the mixture into 100mL Tetrahydrofuran (THF) under the stirring condition, and stirring for 24h; subsequently, 3.278g DPFB (0.125 mol L) was added with stirring -1 ) And stirred for 24h to give a base electrolyte (DPFB/MBA = 1; finally, 1.75g of HFE (50 mol L) are added with stirring -1 ) And (5) stirring the additive for 24 hours to obtain the magnesium battery electrolyte.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Example 7
A method of preparing the electrolyte for a magnesium battery as in example 2, comprising the steps of:
s1, pretreatment of magnesium trifluoromethanesulfonate: drying magnesium trifluoromethanesulfonate in vacuum at 80-120 deg.c for 24-72 hr to eliminate trace water, sealing and setting inside anhydrous and oxygen-free glove box;
s2, pretreatment of an organic ether solvent: adding a 3A molecular sieve activated for 5 hours at 300 ℃ into glycol dimethyl ether while the mixture is hot, and placing the mixture in a glove box for sealed storage;
s3, pretreatment of tri (trimethylsilyl) borate/decafluoro-3-methoxy-2-trifluoromethylpentane (HFE) reagent: drying the 3A molecular sieve at 300 ℃ for 5h, in order to prevent the volatilization of the reagent, cooling the molecular sieve to room temperature, adding the molecular sieve into tris (trimethylsilane) borate and HFE respectively to remove trace moisture, sealing, and standing in an anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, and 16.122g of magnesium trifluoromethanesulfonate (0.5 mol L) was taken -1 ) Slowly adding the mixture into 100mL of glycol dimethyl ether under the stirring condition, and stirring for 30 hours; subsequently, 3.48g of tris (trimethylsilane) borate ester (0.125 mol L) were added with stirring -1 ) Stirring for 24 hours to obtain basic electrolyte; finally, 0.7g of HFE (50 mol L) are added with stirring -1 ) And (5) stirring the additive for 12 hours to obtain the magnesium battery electrolyte.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Example 8
A method of preparing the electrolyte for a magnesium battery as in example 3, comprising the steps of:
s1, pretreatment of magnesium bromide: drying magnesium bromide in vacuum at 80-120 deg.c for 24-72 hr to eliminate trace water, sealing and setting inside anhydrous and oxygen-free glove box;
s2, pretreatment of an organic ether solvent: adding a 3A molecular sieve activated for 5 hours at 300 ℃ into tetraethylene glycol dimethyl ether while the mixture is hot, and placing the mixture in a glove box for sealed storage;
s3, pretreatment of (dimethyl phenylsilyl) boronic acid pinacol ester (DPFB)/tetramethylammonium borohydride reagent: drying the 3A molecular sieve at 300 ℃ for 5h, in order to prevent the volatilization of the reagent, cooling the molecular sieve to room temperature, adding the molecular sieve into DPFB and tetramethylammonium borohydride respectively to remove trace moisture, sealing, and standing in an anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, and 4.603g of magnesium bromide (0.25 mol L) was taken -1 ) Slowly adding the mixture into 100mL of tetraethylene glycol dimethyl ether under the stirring condition, and stirring for 12 hours; subsequently, 1.639g of DPFB (0.125 mol L) were added with stirring -1 ) Stirring for 24 hours to obtain basic electrolyte; finally, 0.178g of tetramethylammonium borohydride (50 mol L) was added with stirring -1 ) And (5) stirring the additive for 8 hours to obtain the magnesium battery electrolyte.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Example 9
A method of preparing the electrolyte for a magnesium battery as in example 4, comprising the steps of:
s1, pretreatment of di-n-butyl magnesium: drying the di-n-butyl magnesium for 24-72 h in vacuum at the temperature of 80-120 ℃ to remove trace moisture, sealing and standing in a glove box without water and oxygen;
s2, pretreatment of an organic ether solvent: adding 3A molecular sieve activated at 300 deg.C for 5 hr in Tetrahydrofuran (THF) and ethylene glycol dimethyl ether, and sealing in glove box;
pretreatment of S3, B-methoxy-10-trimethylsilyl-9-borabicyclo (3.3.2) decane/tetrabutylammonium borohydride reagent: drying the 3A molecular sieve at 300 ℃ for 5h, in order to prevent the volatilization of the reagent, cooling the molecular sieve to room temperature, adding the molecular sieve into B-methoxy-10-trimethylsilyl-9-borabicyclo (3.3.2) decane and tetrabutylammonium borohydride respectively to remove trace moisture, sealing, and standing in an anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, and 3.463g of di-n-butyl were takenMagnesium (0.25 mol L) -1 ) Slowly adding the mixture into a mixed ether solvent of 50mL tetrahydrofuran and 50mL glycol dimethyl ether under the stirring condition, and stirring for 18 hours; subsequently, 2.978g of B-methoxy-10-trimethylsilyl-9-borabicyclo (3.3.2) decane (0.125 mol L) were added with stirring -1 ) Stirring for 20h to obtain basic electrolyte; finally, 0.257g of tetrabutylammonium borohydride (50 mol L) was added with stirring -1 ) And (5) stirring the additive for 14 hours to obtain the magnesium battery electrolyte.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Example 10
A method of making the electrolyte for a magnesium battery as in example 5, comprising the steps of:
s1, pretreatment of magnesium borohydride/magnesium bis (trifluoromethanesulfonyl) imide: drying magnesium borohydride/bis (trifluoromethanesulfonyl) imide magnesium under vacuum at 80-120 deg.c for 24-72 hr to eliminate trace water, sealing and setting inside anhydrous and oxygen-free glove box;
s2, pretreatment of an organic ether solvent: adding 3A molecular sieve activated at 300 deg.C for 5 hr in Tetrahydrofuran (THF), and storing in glove box under sealed condition;
s3, pretreatment of (dimethyl silyl) boric acid pinacol ester (DPFB)/2, 2-dimethoxypropane reagent: drying the 3A molecular sieve at 300 ℃ for 5h to prevent the volatilization of the reagent, cooling the molecular sieve to room temperature, adding the molecular sieve into DPFB and 2, 2-dimethoxypropane respectively to remove trace moisture, sealing, and standing in an anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere of water and oxygen free, taking 0.540g of magnesium borohydride (0.1 mol L) -1 ) +23.380g of magnesium bis (trifluoromethanesulfonyl) imide (0.4 mol L) -1 ) Slowly adding the mixture into 100mL of Tetrahydrofuran (THF) under the stirring condition, and stirring for 24 hours; subsequently, 1.639g of DPFB (0.125 mol L) were added with stirring -1 ) Stirring for 18h to obtain basic electrolyte; finally, 1.041g2, 2-dimethoxypropane (50 mol L) was added with stirring -1 ) Adding the additive, stirring for 10h to obtain the magnesium battery electricityAnd (4) hydrolyzing the liquid.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Comparative example 1
A preparation method of magnesium battery electrolyte comprises the following steps:
s1, pretreatment of bis (diisopropylamino) Magnesium (MBA): drying MBA in vacuum for 24-72 h at the temperature of 80-120 ℃ to remove trace moisture, sealing, and standing in a glove box without water and oxygen;
s2, pretreatment of an organic ether solvent: adding 3A molecular sieve activated at 300 deg.C for 5 hr in Tetrahydrofuran (THF), and storing in glove box;
pretreatment of S3, (dimethylsilyl) boronic acid pinacol ester (DPFB) reagent: drying 3A molecular sieve at 300 deg.C for 5 hr, cooling to room temperature, adding into DPFB to remove trace water, sealing, and standing in anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, and 5.205g of MBA (0.25 mol L) were taken -1 ) Slowly adding the mixture into 100mL of Tetrahydrofuran (THF) under the stirring condition, and stirring for 24 hours; subsequently, 3.28g of DPFB (0.125 mol L) were added with stirring -1 ) And stirred for 24 hours, to obtain a magnesium battery electrolyte (DPFB/MBA = 1.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Comparative example 2
A preparation method of magnesium battery electrolyte comprises the following steps:
s1, pretreatment of bis (diisopropylamino) Magnesium (MBA): drying MBA for 24-72 h in vacuum at 80-120 ℃ to remove trace moisture, sealing, and standing in an anhydrous and oxygen-free glove box;
s2, pretreatment of an organic ether solvent: adding 3A molecular sieve activated at 300 deg.C for 5 hr in Tetrahydrofuran (THF), and storing in glove box under sealed condition;
pretreatment of S3, (dimethylsilyl) boronic acid pinacol ester (DPFB) reagent: drying 3A molecular sieve at 300 deg.C for 5 hr, cooling to room temperature, adding into DPFB to remove trace water, sealing, and standing in anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, taking 3.188g of MBA (0.25 mol L) -1 ) Slowly adding the mixture into 100mL of Tetrahydrofuran (THF) under the stirring condition, and stirring for 24 hours; subsequently, 3.500g DPFB (0.125 mol L) were added with stirring -1 ) And stirred for 24 hours, to obtain a magnesium battery electrolyte (DPFB/MBA = 1.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Comparative example 3
A preparation method of magnesium battery electrolyte comprises the following steps:
s1, pretreatment of bis (diisopropylamino) Magnesium (MBA): drying MBA in vacuum for 24-72 h at the temperature of 80-120 ℃ to remove trace moisture, sealing, and standing in a glove box without water and oxygen;
s2, pretreatment of an organic ether solvent: adding 3A molecular sieve activated at 300 deg.C for 5 hr in Tetrahydrofuran (THF), and storing in glove box;
pretreatment of S3, (dimethylsilyl) boronic acid pinacol ester (DPFB) reagent: drying 3A molecular sieve at 300 deg.C for 5 hr, cooling to room temperature, adding into DPFB to remove trace water, sealing, and standing in anhydrous and oxygen-free glove box;
s4, preparing electrolyte: all reactions were carried out under an inert atmosphere free of water and oxygen, and 3.188g of MBA (0.25 mol L) were taken -1 ) Slowly adding the mixture into 100mL Tetrahydrofuran (THF) under the stirring condition, and stirring for 24h; subsequently, 7.000g of DPFB (0.125 mol L) were added with stirring -1 ) And stirred for 24 hours, to obtain a magnesium battery electrolyte (DPFB/MBA = 2.
All the reactions described above were carried out in a dry glove box with a water/oxygen content below 0.01 ppm.
Electrochemical performance test analysis
1) Magnesium reversible deposition/dissolution and oxidation stability test
The magnesium reversible deposition/dissolution coulombic efficiency and oxidation stability of the magnesium battery electrolyte are respectively tested by a Cyclic Voltammetry (CV) method and a linear voltammetry (LSV) method, and the test instrument is a Shanghai Chenghua CHI 660 electrochemical workstation. The CR2032 button cell is assembled for testing, wherein a positive current collector adopts Stainless Steel (SS), a negative electrode adopts a polished magnesium sheet, a diaphragm adopts a GF/A glass fiber membrane, and the assembled cell is stood for more than 4 hours at room temperature for corresponding testing. The sweep rate of the cyclic voltammetry CV is 25mV/s, and the voltage range is-0.8V-2.0V; the voltage range of the LSV of the linear voltammetry is between open-circuit voltage and 4.5V, and the sweep rate is 5mV/s.
Cyclic voltammetry of the magnesium battery electrolyte prepared in example 6 using stainless steel SS, molybdenum foil or copper foil as a working electrode, the cyclic voltammetry curve is shown in fig. 1, and as can be seen from the analysis in fig. 1, the electrochemically stable potential (vs. Mg/Mg) of the magnesium battery electrolyte prepared in example 6 on stainless steel, molybdenum foil and copper foil is shown 2+ ) The electrolyte is higher, namely 3.2V, 3.1V and 2.8V respectively, so that the stability of the anode of the electrolyte of the magnesium battery is better.
The magnesium battery electrolyte prepared in example 6 was subjected to a linear sweep voltammetry test using stainless steel SS as a working electrode, and the linear sweep voltammetry curve is shown in fig. 2, and as can be seen from the analysis in fig. 2, the magnesium battery electrolyte prepared in example 6 had a deposition overpotential of-210 mV and a dissolution overpotential of 200mV, thus demonstrating that the magnesium battery electrolyte can be reversibly deposited/dissolved.
2) Coulomb efficiency test for magnesium reversible deposition/dissolution performance
The coulombic efficiency of the reversible deposition/dissolution performance of the magnesium battery electrolyte is tested by constant current charging and discharging (CP), and the test instrument is a Wuhan blue charging and discharging tester. The CR2032 button cell is assembled for testing, wherein a positive current collector adopts Stainless Steel (SS), a negative electrode adopts a polished magnesium sheet, a diaphragm adopts a GF/A glass fiber membrane, and the assembled cell is stood for more than 4 hours at room temperature for testing. Charge and discharge test CThe discharge time of P is 30min, the cut-off voltage of charging is 2V, and the current density is 0.1mA/cm 2 。
The coulombic efficiency of the electrolyte for the magnesium battery prepared in example 6 was measured using stainless SS as a working electrode, as shown in fig. 3, and it can be seen from the analysis in fig. 3 that the electrolyte for the magnesium battery prepared in example 6 was 0.1mA/cm 2 The average deposition/dissolution efficiency of 200 cycles under the current density of the electrolyte reaches up to 99.5 percent, thereby proving that the electrolyte of the magnesium battery has high coulombic efficiency and good cycle performance.
3) Test of polarization Properties
The polarization performance of the magnesium battery electrolyte is tested by constant current charge and discharge (CP), and the testing instrument is a Wuhan blue charge and discharge tester.
The method specifically comprises the following steps: the magnesium battery electrolyte prepared in example 6 was tested by assembling CR2032 button Mg// Mg symmetrical batteries, wherein both the positive and negative electrodes used polished smooth magnesium sheets (Mg), the separator used GF/a glass fiber membrane, and the assembled batteries were left to stand at room temperature for more than 4 hours before testing. The discharge time of the CP is 30min, the charge time is 30min, and the current is 0.05mA/cm 2 ～2mA/cm 2 。
The electrolyte of the magnesium battery prepared in the example 6 is assembled into a Mg// Mg symmetrical battery at 0.1mA/cm 2 The long-circulating polarization curve at current density is shown in fig. 4.
As can be seen from the analysis in FIG. 4, the electrolyte for the magnesium battery prepared in example 6 was 0.1mA/cm 2 The initial polarization potential is as low as 180mV, the polarization potential after 800 cycles is increased to 210mV, and the overpotential is not increased significantly, thus proving that the magnesium battery electrolyte has small polarization and excellent cycle performance.
The rate polarization curves of Mg// Mg symmetrical cells assembled with the magnesium cell electrolyte prepared in example 6 at different current densities are shown in FIG. 5.
From the analysis in FIG. 5, it can be seen that when the current density is from 0.05mA/cm 2 Gradually increased to 2mA/cm 2 While, the polarization potential of the electrolyte for the magnesium battery prepared in example 6 increased from 230mV to no more than about 400mV, thus demonstrating the magnesium potentialThe cell electrolyte can withstand a greater current density.
The electrolyte solutions of the magnesium batteries manufactured in examples 7 to 10 and comparative examples 1 to 3 were tested for their relevant electrochemical properties according to the same test methods as described above, and the results are shown in table 1.
TABLE 1 electrochemical Performance test results for magnesium Battery electrolytes
| 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 |
From the comprehensive analysis in table 1, the magnesium battery electrolyte of the invention has the advantages of high electrochemical window, high deposition/dissolution coulomb efficiency, long cycle life and the like.
In summary, the magnesium battery electrolyte of the present invention is prepared by adjusting the ratio of the magnesium salt to the organic boric acid and derivatives thereof, and introducing the F-containing additive or the water removal additive to achieve the electrolyte with high anode stability, aiming at the problems that most of the magnesium battery electrolytes contain chlorine and have corrosiveness and have a low voltage window in the prior art. The magnesium battery has the advantages of wide electrochemical window, higher deposition/dissolution efficiency, low overpotential, simple preparation and low cost. Most importantly, the magnesium battery electrolyte does not contain corrosive ion components, does not corrode a current collector and a battery shell, and is favorable for prolonging the service life of the battery. In a word, the magnesium ion electrolyte has good commercialization prospect, and has popularization and application values in the technical field of magnesium ion batteries.
The above embodiments are merely illustrative of the principles of the present invention and its efficacy, and are not intended to limit the present application. Any person skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present application. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed in the present application shall be covered by the claims of the present application.
Claims (10)
1. The magnesium battery electrolyte is characterized by comprising a magnesium salt electrolyte, organic boric acid and derivatives thereof, an organic ether solvent and an additive, wherein the magnesium battery electrolyte does not comprise a chlorine-containing compound additive, the magnesium salt electrolyte is a non-nucleophilic electrolyte, and the additive is a water-removing additive.
2. The magnesium battery electrolyte of claim 1, wherein the magnesium salt electrolyte is bis (diisopropylamino) magnesium, magnesium borohydride, n-butylmagnesium, magnesium bis (trifluoromethanesulfonyl) imide (Mg (TFSI) 2 ) And magnesium triflate.
3. The magnesium battery electrolyte of claim 1, wherein the organic boronic acid and its derivatives are one or more of (dimethylbenzylsilane) boronic acid pinacol ester, tris (trimethylsilane) boronate ester, and B-methoxy-10-trimethylsilyl-9-borabicyclo (3.3.2) decane.
4. The magnesium battery electrolyte as claimed in claim 1, wherein the organic ether solvent is one or more of tetrahydrofuran, glyme, diglyme, triglyme and tetraglyme;
the additive is decafluoro-3-methoxy-2-trifluoromethyl pentane, 2-dimethoxy propane or quaternary ammonium borohydride salt;
the quaternary ammonium borohydride salt comprises one or more of tetramethyl ammonium borohydride, tetraethyl ammonium borohydride and tetrabutyl ammonium borohydride.
5. The magnesium battery electrolyte of claim 1 wherein the magnesium salt electrolyte is bis (diisopropylamino) magnesium; the organic boric acid and the derivative thereof are (dimethyl phenyl silyl) boric acid pinacol ester; the additive is decafluoro-3-methoxy-2-trifluoromethyl pentane.
6. The magnesium battery electrolyte as claimed in claim 1, wherein the molar ratio of the magnesium salt electrolyte to the organic boric acid and derivatives thereof is 1.
7. The magnesium battery electrolyte as claimed in claim 1, wherein the additive accounts for 1 to 5 mass percent of the magnesium battery electrolyte.
8. A method of preparing a magnesium battery electrolyte as claimed in any one of claims 1 to 7, comprising the steps of:
respectively removing moisture in magnesium salt electrolyte, organic boric acid and derivatives thereof, organic ether solvent and additives;
mixing a magnesium salt electrolyte and an organic ether solvent under the anhydrous and anaerobic conditions, sequentially adding organic boric acid and derivatives thereof and an additive under the stirring condition, and stirring for 8 to 30h to obtain the magnesium battery electrolyte.
9. The method for preparing the magnesium battery electrolyte according to claim 8, wherein the organic boric acid and the derivatives thereof, the organic ether solvent and the liquid additive are subjected to water removal by using a 3A molecular sieve activated at 300 ℃ for 5 hours, the magnesium salt electrolyte and the fixed additive are subjected to vacuum drying, and the vacuum drying is carried out under the conditions of 80 to 120 ℃ for 24 to 72h.
10. A magnesium battery, wherein the electrolyte in the magnesium battery is the magnesium battery electrolyte according to any one of claims 1 to 7.
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