Iron‐Based NASICON‐Type Na4Fe3(PO4)2(P2O7) Cathode for Zinc‐Ion Battery: Zn2+/Na+ Co‐Intercalation Enabling High Capacity

The development of high-performance cathode materials for aqueous zinc-ion batteries (ZIBs) based on nontoxic and earth-abundant elements remains a great challenge. This study introduces the iron-based NASICON-type material Na4 Fe3 (PO4 )2 (P2 O7) with carbon layer (NFPP@C) as a cathode material for ZIBs. When Zn2+ /Na+ dual ion electrolyte is employed, NFPP@C shows a high capacity of 114.4 mAh g-1 with two voltage plateaus, excellent rate capability (95 mAh g-1 at 2 A g-1 ), and long-term cycling stability (66.4 mAh g-1 after 1800 cycles at 1 A g-1 ). The outstanding electrochemical performance is ascribed to the synergistic use of NFPP@C and dual ion electrolyte. The NASICON-structure and carbon layer of NFPP@C enable fast ion and electron transport, whereas Na+ in the electrolyte reduces the concentration gradient between the electrode and electrolyte, and thus inhibits excessive extraction of Na+ from NFPP, maintaining structural stability. Moreover, Zn2+ /Na+ co-intercalation in NFPP@C brings two potential platforms and enhanced capacity.