Nanostructured Layered Cathode for Rechargeable Mg-Ion Batteries

Nanostructured bilayered V₂O₅ was electrochemically deposited within a carbon nanofoam conductive support. As-prepared electrochemically synthesized bilayered V₂O₅ incorporates structural water and hydroxyl groups, which effectively stabilizes the interlayers and provides coordinative preference to the Mg²⁺ cation in reversible cycling. This open-framework electrode shows reversible intercalation/deintercalation of Mg²⁺ ions in common electrolytes such as acetonitrile. Using a scanning transmission electron microscope we demonstrate that Mg²⁺ ions can be effectively intercalated into the interlayer spacing of nanostructured V₂O₅, enabling electrochemical magnesiation against a Mg anode with a specific capacity of 240 mAh/g. We employ HRTEM and X-ray fluorescence (XRF) imaging to understand the role of environment in the intercalation processes. A rebuilt full cell was tested by employing a high-energy ball-milled Sn alloy anode in acetonitrile with Mg(ClO₄)₂ salt. XRF microscopy reveals effective insertion of Mg ions throughout the V₂O₅ structure during discharge and removal of Mg ions during electrode charging, in agreement with the electrode capacity. We show using XANES and XRF microscopy that reversible Mg intercalation is limited by the anode capacity. (Figure Presented).