Iron-Based NASICON-Type Na Fe (PO ) (P O ) Cathode for Zinc-Ion Battery: Zn /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 Na Fe (PO ) (P O7) with carbon layer (NFPP@C) as a cathode material for ZIBs. When Zn /Na dual ion electrolyte is employed, NFPP@C shows a high capacity of 114.4 mAh g with two voltage plateaus, excellent rate capability (95 mAh g at 2 A g ), and long-term cycling stability (66.4 mAh g after 1800 cycles at 1 A g ). 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, Zn /Na co-intercalation in NFPP@C brings two potential platforms and enhanced capacity.