A Fluorinated Alkoxyaluminate Electrolyte for Magnesium-Ion Batteries

Abstract

he lack of electrolytes that simultaneously possess highCoulombic efficiency, conductivity, and voltage stability has hindered thedeployment of rechargeable magnesium-ion batteries. With few exceptions,the tenacious oxide layer on magnesium metal has limited the scope ofresearch to halide ion-based electrolytes, which help activate the electrodesurface but also limit the working voltage window considerably. Herein, wedemonstrate a new class of magnesium electrolytes based onfluoroalkox-yaluminate anions synthesized via a facile and scalable method and itsincorporation in a full battery cell. Mixtures of magnesium and aluminumfluoroalkoxides in ethereal solvents result in solutions that can reversiblydeposit magnesium metal with near unit efficiency in addition to achieving suitable oxidative stabilities (>3.5 V vs Mg/Mg2+on glassy carbon and gold) and conductivities (>6 mS cm−1).