Intercalation of Magnesium into a Layered Vanadium Oxide with High Capacity

While alpha-V2O5 has traditionally been considered as a promising oxide to reversibly intercalate high levels of Mg2+ at high potential, recent reports indicate that previously observed electrochemical activity is dominated by intercalation of H+ rather than Mg2+, even in moderately dry nonaqueous electrolytes. Consequently, the inherent functionality of oxides to intercalate Mg2+ remains in question. By conducting electrochemistry in a chemically and anodically stable ionic liquid electrolyte, we report that, at 110 degrees C, layered alpha-V2O5 is indeed capable of reversibly intercalating 1 mol Mg2+ per unit formula, to accumulate capacities above 280 mAh g(-1). Multimodal characterization confirmed intercalation of Mg2+ by probing the elemental, redox, and morphological changes undergone by the oxide. After cycling at 110 degrees C, the electrochemical activity at room temperature was significantly enhanced. The results renew prospects for functional Mg rechargeable batteries surpassing the levels of energy density of current Li-ion batteries.