Highly Efficient Non-Nucleophilic Mg(CFSO)-Based Electrolyte for High-Power Mg/S Battery.

The application of high-energy Mg/S batteries was obstructed by the insufficiency of low-cost and non-nucleophilic electrolyte. In this work, a non-nucleophilic electrolyte was prepared by facilely dissolving Mg(CFSO), MgCl, and AlCl in 1,2-dimethoxyethane (DME). The equilibrium species of the MTB electrolyte mainly comprise [Mg(μ-Cl)(DME)] and [(CFSO)AlCl], which are generated by dehalodimerization reaction and Lewis acid-base reaction, respectively. The electrolyte exhibits a highly efficient reversible Mg deposition/dissolution, low overpotential of around 250 mV, and good oxidative stability up to 3.5 V after conditioning. The conditioning process that the active [Mg(μ-Cl)(DME)] species transforms into [Mg(μ-Cl)(μ-Cl)(DME)] was demonstrated, owing to the irreversible deposition of Al on Mg foil. More importantly, this electrolyte exhibited good compatibility and kinetics for reversible Mg/MgS redox, resulting in a high specific capacity of 866 mAh g at 200 mA g and high power density of 550 W kg. This work offers a new direction for low-cost, non-nucleophilic electrolyte and paves the way to explore high-power Mg/S batteries.