Room Temperature Magnesium Electrodeposition from Glyme-Coordinated Ammonium Amide Electrolytes

Abstract

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.