A Novel and Highly Efficient Indolyl‐Based Electrolyte for Mg Batteries

Magnesium‐based batteries are one of the most promising candidates as postlithium electrochemical energy storage devices. Despite considerable research progress, suitable electrolytes supporting long‐term reversible stripping/deposition of magnesium metal in a low content or halide‐free electrolyte are still of great interest. Moreover, the electrolytes should possess certain properties to be a good match with candidate cathode materials. Herein, the electrochemical performance of a novel indolyl‐based electrolyte is presented. Theoretical modeling combined with NMR analysis identifies the magnesium species in the electrolyte. Reversible stripping/deposition of Mg metal in indolyl‐based electrolyte shows long‐term cycling with high coulombic efficiency of >99.5% and yields dendrite‐free magnesium deposition in compact and smooth layers. The X‐ray diffraction shows different preferential structural orientations depending on the electrode substrate. Finally, a proof‐of‐concept Mg║Mo6S8 full cell using the newly developed electrolyte is proposed. The novel indolyl‐based electrolyte allows long‐term dendrite‐free reversible deposition/dissolution of Mg metal with high coulombic efficiency of >99.5%. The analysis of Mg species reveals the formation of a Schlenk‐type equilibrium, with (thf)4 Mg(Ind)Br as the main bulk species, in line with the theoretical calculation of solvation–desolvation energies. A proof‐of‐concept Mg║Mo6S8 full cell using the newly developed electrolyte is proposed.