β-V 2 O 5 as Magnesium Intercalation Cathode.

Magnesium batteries have attracted great attention as an alternative to Li-ion batteries but still suffer from limited choice of positive electrode materials. V 2 O 5 exhibits high theoretical capacities, but previous studies have been mostly limited to α-V 2 O 5 . Herein, we report on the β-V 2 O 5 polymorph as a Mg intercalation electrode. The structural changes associated with the Mg 2+ (de-) intercalation were analyzed by a combination of several characterization techniques: in situ high resolution X-ray diffraction, scanning transmission electron microscopy, electron energy-loss spectroscopy, and X-ray absorption spectroscopy. The reversible capacity reached 361 mAh g -1 , the highest value found at room temperature for V 2 O 5 polymorphs.