On the cathode material of Na4Fe3-xCox(PO4)2P2O7 towards high discharge capacity and long-cycle stability for sodium-ion batteries

Sodium-ion batteries have garnered significant attention due to their low cost, high safety, and excellent low-temperature performance. In particular, the Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) cathode material has been extensively studied, owing to its cost-effectiveness and environmental friendliness. However, its practical application is severely limited by insufficient energy density. This study employs a solid-state ball-milling method to synthesize a series of cobalt-doped NFPP materials of Na 4 Fe 3-x Co x (PO 4 ) 2 P 2 O 7 . Comprehensive experimental characterizations and electrochemical analyses of the prepared half-cells demonstrate that the optimized Na 4 Fe 2.8 Co 0.2 (PO 4 ) 2 P 2 O 7 cathode material exhibits a high initial discharge capacity (119.35 mAh g −1 at 0.1 C), excellent rate capability (79.26 mAh g −1 at 30 C), and remarkable long-cycle stability (approximately 96.91% capacity retention after 1500 cycles at 10 C). This work provides the community with a feasible strategy for developing high-performance sodium-ion batteries.