Chloride-Free Electrolyte Based on Tetrabutylammonium Triflate Additive for Extended Anodic Stability in Magnesium Batteries

Rechargeable magnesium batteries (RMBs) have been proposed as a promising alternative to currently commercialized lithium-ion batteries. However, Mg anode passivation in conventional electrolytes necessitates the use of highly corrosive Cl- ions in the electrolyte. Herein for the first time, we design a chloride-free electrolyte for RMBs with magnesium bis(hexamethyldisilazide) (Mg(HMDS)2) and magnesium triflate (Mg(OTf)2) as the main salts and tetrabutylammonium triflate (TBAOTf) as an additive. The TBAOTf additive improved the dissolution of Mg salts, consequently enhancing the charge-carrying species in the electrolyte. COMSOL studies further revealed desirable Mg growth in our modulated electrolyte, substantiated by homogeneous electric flux distribution across the electrolyte-electrode interface. Post-mortem chemical composition analysis uncovered a MgF2-rich solid electrolyte interphase (SEI) that facilitated exceptional Mg deposition/dissolution reversibility. Our study illustrates a highly promising strategy for synthesizing a corrosion-free and reversible Mg battery electrolyte with a widened anodic stability window of up to 4.43 V.