Zero-strain Na4Fe7(PO4)6 as a novel cathode material for sodium–ion batteries†
Abstract
We report for the first time a zero-strain cathode, Na4Fe7(PO4)6, for sodium–ion batteries (SIBs). This new iron-based polyanionic cathode delivers a reversible capacity of 66.5 mA h g−1 at 5 mA g−1 with almost 100% capacity retention over 1000 cycles under 200 mA g−1, and the outstanding performance benefits from single-phase-transition processes with a tiny volume change of only ∼0.24%.