The combination of a magnesium anode with a sulfur cathode is one of the most promising electrochemical couples because of its advantages of good safety, low cost, and a high theoretical energy density. However, magnesium sulfur batteries are still in a very early stage of research and development, and the discovery of suitable electrolytes is the key challenge for further improvement. Here, a new preparation method for non-nucleophilic electrolyte solutions using a two-step reaction in one-pot is presented, which provides a feasible way to optimize the physiochemical properties of the electrolyte for the application in magnesium sulfur batteries. The fi rst use of modifi ed electrolytes in glymes and binary solvents of glyme and ionic liquid shows benefi cial effects on the performance of magnesium sulfur batteries. New insights into the reaction mechanism of electrochemical conversion between magnesium and sulfur are also investigated.

Easily synthesized fluorinated magnesium alkoxyborates with non-corrosive and chemically stable features show high electrochemical performance as magnesium ion conducting salts.

The rechargeable magnesium (Mg) battery has been considered a promising candidate for future battery generations due to unique advantages of the Mg metal anode. The combination of Mg with a sulfur cathode is one of the attractive electrochemical energy storage systems that use safe, low-cost, and sustainable materials and could potentially provide a high energy density. To develop a suitable electrolyte remains the key challenge for realization of a magnesium sulfur (Mg–S) battery. Herein, we demonstrate that magnesium tetrakis­(hexafluoroisopropyloxy) borate Mg­[B­(hfip)4]2 (hfip = OC­(H)­(CF3)2) satisfies a multitude of requirements for an efficient and practical electrolyte, including high anodic stability (>4.5 V), high ionic conductivity (∼11 mS cm–1), and excellent long-term Mg cycling stability with a low polarization. Insightful mechanistic studies verify the reversible redox processes of Mg–S chemistry by utilizing Mg­[B­(hfip)4]2 electroylte and also unveil the origin of the voltage hysteresis in Mg–S batteries.

A novel Ca electrolyte with a broad electrochemical window and high ionic conductivity is demonstrated.