A non-nucleophilic mono-Mg2+ electrolyte for rechargeable Mg/S battery

Abstract Rechargeable magnesium/sulfur (Mg/S) battery is widely regarded as one of the most promising candidates for post-lithium batteries. However, a key factor restricting its application is the lack of a proper Mg electrolyte. Herein, we developed a coordination pre-protection strategy to synthesize a mono-magnesium ion, non-nucleophilic electrolyte capable of highly reversible Mg electrodeposition (up to 100% coulombic efficiency), enduring high current density (5 mA cm−2), and enabling a stable electrochemical potential window over 3.5 V at room temperature. Using the as-prepared electrolyte, Mg/S cells with a good cycling stability over 100 cycles were achieved. For the first time, in-situ microscopic observation of the electrochemical magnesium deposition/stripping process in this new electrolyte was investigated.