Abstract
We report the electrochemical properties vs. Na of the layered NaxVO2 phases having either octahedral or trigonal prismatic symmetries. Both phases can reversibly insert 0.5 Na atom per unit formula leading to sustained reversible capacities of nearly 120 mAh/g. Their voltage profile shows numerous voltage steps being mainly associated to subtle ordering of the Na ions within the layers while each phase preserves its initial structure through the entire Na insertion–deinsertion process.