Electrochemical Na-Deintercalation from NaVO2

Abstract

This<sup> </sup>paper describes the preparation of Na<sub>x</sub>VO<sub>2</sub> phases by means of<sup> </sup>electrochemical deintercalation. The curves V = f(x) show that the process is<sup> </sup>reversible up to x = 0.5 and they indicate the presence of<sup> </sup>multiple single phase domains in the range 1 < x < 0.5. Two single<sup> </sup>phases have been successfully isolated for Na<sub>1/2</sub>VO<sub>2</sub> and Na<sub>2/3</sub>VO<sub>2</sub> compositions;<sup> </sup>we report here the first X-ray powder diffraction measurements of<sup> </sup>these phases. They present a O'3-type monoclinic distortion of the<sup> </sup>O3 rhombohedral phase observed for Na<sub>1</sub>VO<sub>2</sub>. The evolution of cell<sup> </sup>parameters with sodium deintercalation is comparable with other A<sub>x</sub>MO<sub>2</sub> layered<sup> </sup>oxides.