Electrochemical Conditioning-Free and Water-Resistance of the hybrid AlCl₃/MgCl₂/Mg(TFSI)₂ Electrolytes for Rechargeable Mg Batteries.

Rechargeable magnesium batteries are a promising alternative to Li-based energy storage because of their abundant and inexpensive components. The high sensitivity and reactivity of the organic Mg2+ electrolyte makes their development challenging. Herein, we develop a new hybrid electrolyte, based on three simple inorganic salts of MgCl2, AlCl3, and Mg(TFSI)(2). The electrolyte exhibits unprecedented electrochemical performance for reversible deposition and stripping of Mg, with Coulombic efficiency up to 97%, overpotential down to 0.10V, good stability especially for aluminum and stainless-steel current collectors. It maintained its activity even after introducing 2000ppm water and it could be prepared from impure chemicals. A full cell with the hybrid electrolyte and Mg foil as anode, Mo6S8 as cathode gave a specific capacity of 98mAhg(-1) and maintained 94% capacity after 100cycles at a rate of 0.20C, indicating the good compatibility of the hybrid electrolyte.