A bifunctional Na-deficient strategy induced pure phase Na4−xFe3(PO4)2P2O7 cathode with high capacity for sodium-ion batteries

This study proposes a Na-deficient strategy for the structural modulation of NFPP, successfully synthesizing pure-phase Na 4− x Fe 3 (PO 4 ) 2 (P 2 O 7 ) with a near-theoretical specific capacity of 127.2 mA h g −1 at 0.1C.