Room Temperature Magnesium Electrodeposition from Glyme-Coordinated Ammonium Amide Electrolytes

We prepared less volatile and halide-free electrolytes for room temperature non-dendritic magnesium (Mg) electrodeposition by mixing a Mg 2+ -amide-containing ionic liquid (IL) with equimolar glyme (Mg 2+ +IL : glyme = 1:1). Raman spectroscopy suggested that in the equimolar mixture most glyme molecules are coordinated to Mg 2+ cations and/or IL cations, which is also supported by a single crystal X-ray diffraction study. The glyme-coordinated IL electrolytes showed sizable redox currents (order of mA cm –2 ), while aging deterioration of electrochemical properties was observed for the triglyme mixture due to partial bath decomposition. The tetraglyme-coordinated IL electrolyte enabled flat electrodeposition of Mg with a metallic luster and showed with very high anodic stability (ca. +4 V vs. Mg) because of decrease in uncoordinated glymes, which can be used for high-voltage Mg ion batteries.