Sodium vanadium nitridophosphate Na3V(PO3)3N as a high-voltage positive electrode material for Na-ion and Li-ion batteries

•Na3V(PO3)3N shows the highest operation voltage for VIV/III-based Na-ion cathodes.•Na3V(PO3)3N delivers stable capacity with very low voltage hysteresis.•Similar performances are obtained for both lithium and sodium half-cells.•The second Na extraction is predicted beyond the electrolytes' stability window.

We report the preparation and electrochemical properties of Na3V(PO3)3N made by ammonolysis. Na3V(PO3)3N is reversibly oxidized to Na2V(PO3)3N at high voltage (4.0 V vs. Na+/Na0 and 4.1 V vs. Li+/Li0) with an unusually small difference in the insertion/extraction voltage between both alkali metal reference electrodes. In both cases, the voltage hysteresis is extremely small (~ 0.035 V vs. sodium and ~ 0.065 V vs. lithium), which suggests facile migration of alkali cations within the structure. Further oxidation to NaV(PO3)3N is predicted to occur beyond the voltage stability window of the electrolytes.

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