α-MnO2 as a cathode material for rechargeable Mg batteries

► We show that nano-sized α-MnO2 has a reversible capacity over 240 mAh/g with Mg ions. ► The reversibility of α-MnO2 with Mg ions was verified by ex-situ XPS and XAS measurements. ► α-MnO2, as described above, can be considered as a cathode candidate for rechargeable Mg batteries.