High-capacity nanostructured manganese dioxide cathode for rechargeable magnesium ion batteries

Abstract Nanostructured λ-MnO 2 and α-MnO 2 are investigated for use in rechargeable Mg ion battery (MIB) cathodes. In order to prepare nanosized particles, the manganese dioxides are prepared by the acid treatment of spinel MgMn 2 O 4 synthesized using the Pechini method. X-ray diffraction analysis indicates that the resulting MnO 2 consists of multiple phases, λ-MnO 2 , α-MnO 2 , and β-MnO 2 , depending on the leaching time in acid solution. Upon the first charge–discharge cycle in acetonitrile electrolyte, the λ-MnO 2 based electrode shows larger reversible capacity of ∼330 mAh g −1 compared to an electrode containing a large amount of α-MnO 2 . This enhanced capacity is associated with the facile charge-transfer reaction of Mg ions at the MnO 2 /electrolyte interfaces. The capacity fading of MnO 2 in different electrolytes is also discussed in terms of the formation of a surface layer at the electrode/electrolyte interface during the charging process.