Electrolyte Solutions for Rechargeable Magnesium Batteries Based on Organomagnesium Chloroaluminate Complexes

Abstract

Magnesium can be reversibly deposited from ethereal solutions of Grignard salts of the RMgX type ( R = alkyl , aryl groups, and X = halides : Cl, Br), and complexes of the Mg ( AX 4 − n R n ′ R n ″ ′ ) 2 type ( A = Al , B; X = Cl , Br; R, R ′ = alkyl or aryl groups, and n ′ + n ″ = n ) . These complexes can be considered as interaction products between R 2 Mg bases and AX 3 − n R n Lewis acids. The use of such complexes in ether solvents enables us to obtain solutions of reasonable ionic conductivity and high anodic stability, which can be suitable for rechargeable Mg battery systems. In this paper we report on the study of variety of Mg ( AX 4 − n R n ) 2 complexes, where A = Al , B, Sb, P, As, Fe, and Ta; X = Cl , Br, and F; and R = butyl , ethyl, phenyl, and benzyl (Bu, Et, Ph, and Bz, respectively) in several solvents, including tetrahydrofuran (THF), 2Me-THF, 1-3 dioxolane, diethyl ether, and polyethers from the “glyme” family, including dimethoxyethane (glyme), ( CH 3 OCH 2 CH 2 ) 2 O ( diglyme ) , and CH 3 ( OCH 2 CH 2 ) 4 OCH 3 (tetraglyme), as electrolyte solutions for rechargeable magnesium batteries. It was found that Mg ( AlCl 4 − n R n ′ R n ″ ′ ) 2 complexes (R, R ′ = Et , Bu and n ′ + n ″ = n ) in THF or glymes constitute the best results in terms of the width of the electrochemical window ( > 2 V ) , from which magnesium can be deposited reversibly. These solutions were found to be suitable for use in rechargeable magnesium batteries. A variety of electrochemical and spectroscopic studies showed that these solutions have a complicated structure, which is discussed in this paper. It is also clear from this work that Mg deposition-dissolution processes in these solutions are far from being simple reactions of Mg / Mg + 2 redox couple. The conditions for optimized Mg deposition-dissolution processes are discussed herein. © 2001 The Electrochemical Society. All rights reserved.

AlCl3-dissolved Diglyme as Electrolyte for Room-Temperature Aluminum Electrodeposition

“…glymes receive attention as relatively safe solvents for lithium and magnesium ion batteries, because they have high boiling points above 150°C and relatively low volatilities at RT in addition to their good chelating ability. [23][24][25][26] Furthermore, previous NMR studies have indicated sizable amount of ionic Al species in glyme solutions, 27 possibly giving good conductivities. To the best of our knowledge, however, there have been no reports on their electrochemical properties.…”

Evaluation of (CF3SO2)2N−(TFSI) Based Electrolyte Solutions for Mg Batteries

“…Magnesium is a natural candidate anode material for "next generation" rechargeable batteries due to its high volumetric capacity (3833 mAh/cm 3 ), low reduction potential (−2.3 V) wide abundance, and low price. 1 Rechargeable Mg battery research had been developing very slowly since the 1920's but had recently gained a big momentum.…”

“…2,3 Unfortunately, even the best DCC electrolyte solution does not possess the minimum requirement needed for next generation rechargeable magnesium batteries, e.g. wide electrochemical stability window (>2.2 V), chemical stability and safety.…”

Effect of Alkali and Alkaline Earth Metal Salts on Suppression of Lithium Dendrites

“…21 Reversible magnesium deposition has been achieved in from Grignard based solutions and some ionic liquids electrolytes. [22][23][24][25][26] The remaining alkaline earth metals, calcium, strontium and barium, have not been studied alone or as additives in lithium deposition. Calcium, strontium, and barium are used in phosphate and carbonate coatings for biocompatibility, but these coatings are formed by electrochemically assisted deposition, not a direct reduction of the metal.…”