Intercalation of Magnesium into a Layered Vanadium Oxide with High Capacity

While α-V 2 O 5 has traditionally been considered as a promising oxide to reversibly intercalate high levels of Mg 2+ at high potential, recent reports indicate that previously observed electrochemical activity is dominated by intercalation of H + rather than Mg 2+, even in moderately dry nonaqueous electrolytes. Consequently, the inherent functionality of oxides to intercalate Mg 2+ remains in question. By conducting electrochemistry in a chemically and anodically stable ionic liquid electrolyte, we report that, at 110 °C, layered α-V 2 O 5 is indeed capable of reversibly intercalating 1 mol Mg 2+ per unit formula, to accumulate capacities above 280 mAh g –1 . Multimodal characterization confirmed intercalation of Mg 2+ by probing the elemental, redox, and morphological changes undergone by the oxide. After cycling at 110 °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.