High‐Energy and Long‐Life Na <sub>3</sub> V <sub>2</sub> (PO <sub>4</sub> ) <sub>2</sub> F <sub>3</sub>
Sodium‐ion batteries are promising for sustainable energy storage, but their energy density still lags behind lithium‐ion systems. Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) is an attractive high‐voltage polyanionic cathode, but fluorine loss generates low‐voltage Na 3 V 2 (PO 4 ) 3 impurities that lower energ...