A combined first principles and experimental study on Na3V2(PO4)2F3 for rechargeable Na batteries

Abstract

The electrochemical properties of Na₃V₂(PO₄)₂F₃ 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 Na_3−xV₂(PO₄)₂F₃ 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 (∼1%) and unit cell volume (∼2%) which results in a good cycle performance. It is further noticed that the desodiated phase is thermally stable up to 550 °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 Na_3−xV₂(PO₄)₂F₃ upon battery cycling.