Fig. 4: Voltage profiles for vanadium-based positive electrodes.

Potential vs. specific capacity plots for Na3V2(PO4)3, Na3V2(PO4)2F3, β-NaVP2O7 normalized to the theoretical specific capacity per one-electron V3+↔V4+ transition from experimental data59,60,61. For k-NaVPO4F, the experimental discharge profile is presented for comparison. For all the materials, the theoretical specific capacity values are reported.