A combined first principles and experimental study on Na3V2(PO4)(2)F-3 for rechargeable Na batteries

Abstract

The electrochemical properties of Na3V2(PO4)(2)F-3 in a Na rechargeable battery were investigated through a combined computational and experimental study. Ex situ XRD results indicate that the reversible sodiation/desodiation occurs via one phase reaction and the structure of Na3-xV2(PO4)(2)F-3 remains quite stable upon extraction and insertion of sodium. Notable is that the one phase reaction is accompanied by the negligible variation in lattice parameters (similar to 1%) and unit cell volume (similar to 2%) which results in a good cycle performance. It is further noticed that the desodiated phase is thermally stable up to 550 degrees C implying the excellent safety characteristic of the charged electrode. The first principles calculations elucidate the mechanisms of the structural evolution and the electrochemical behavior of Na3-xV2(PO4)(2)F-3 upon battery cycling.