Benzenethiolate-based solutions for rechargeable magnesium battery electrolytes

Abstract

The benzenethiolate-based solutions (RSMgCl)n-AlCl3/tetrahydrofuran (THF) (R=4-methylbenzene, 4-isopropylbenzene, 4-methoxybenzene; n=1, 1.5, 2, respectively) were obtained by the simple reaction of benzenethiol compounds with the Grignard reagent C2H5MgCl/THF and AlCl3 in THF, and the electrochemical performance as the rechargeable magnesium battery electrolytes are reported. First, 4-methyl-benzenethiolate magnesium chloride (MBMC)/THF, 4-isopropylbenzenethiolate magnesium chloride (IPBMC)/THF, and 4-methoxybenzenethiolate magnesium chloride (MOBMC)/THF solutions (termed as RSMgCl/THF) were synthesized by the reaction of 4-methylbenzenethiol, 4-isopropylbenzenethiol, and 4-methoxybenzenethiol compounds, respectively, with C2H5MgCl/THF via a hydrogen metal-radical exchange with rapid evolution of ethane gas. Furthermore, (RSMgCl)n-AlCl3/THF solutions were obtained by the reaction of RSMgCl/THF with AlCl3/THF at different molar ratios of RSMgCl:AlCl3. The benzenethiolate-based solutions as electrolytes for rechargeable magnesium batteries were characterized in term of anodic stability and reversibility of magnesium deposition-dissolution using cyclic voltammetry and galvanostatic charge/discharge techniques. Furthermore, the compatibility of the solutions with Mo6S8 cathode material was verified using coin cells with a Mo6S8 cathode, Mg anode, and benzenethiolate-based electrolyte. It is concluded that both the substituents on benzenethiol and the ratio of RSMgCl:AlCl3 have an effect on the electrochemical performance. 0.5 mol·L-1 (IPBMC)1.5-AlCl3/ THF shows the best electrochemical performance with 2.4 V (vs Mg/Mg2+) anodic stability, a low voltage for magnesium deposition-dissolution, a high cycling reversibility, and good compatibility with the Mo6S8 cathode. Moreover, the air insensitive character and easy preparation make it a promising candidate for rechargeable battery electrolytes. © Editorial office of Acta Physico-Chimica Sinica.