Na3V2O2x(PO4)2F3−2x: a stable and high-voltage cathode material for aqueous sodium-ion batteries with high energy density

Abstract

The reversible electrochemical activity of the Na₃V₂O_2x(PO₄)₂F_3−2x compound in an aqueous solution is reported for the first time. Na₃V₂O_2x(PO₄)₂F_3−2x with multi-walled carbon nanotubes (MWCNTs) exhibits a long-term stability for up to 1100 cycles in aqueous electrolytes. Two different types of Na-ion full-cells demonstrate the feasibility of the Na₃V₂O_2x(PO₄)₂F_3−2x/MWCNT composite as a cathode for aqueous sodium-ion batteries. A high full-cell voltage of 1.7 V and a high energy density of 84 W h kg⁻¹ were achieved using Zn metal as an anode.