Toward High Performance of Na4Fe3(PO4)2P2O7 Cathode via Constructing a Porous Structure for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are a promising alternative to lithium-ion batteries for grid-scale energy-storage systems due to their low cost and abundant resource. Herein, Na4Fe3(PO4)2P2O7 with a porous structure was fabricated by a mechanochemical method. The porous structure and the uniform carbon coating layer of the material are beneficial to the electrolyte infiltration for better electron/ion transfer. The in situ and ex situ XRD analyses reveal that the cathode material undergoes an imperfect solid-resolution reaction during the charge/discharge process. The robust structural stability and high reversibility of the cathode material are attributed for the excellent rate performance and the long-term cycling life. The cathode material gives a high reversible capacity (124.5 mAh g–1 at 0.1 C), a superior rate performance (97.6 mAh g–1 at 50 C), and an excellent ultralong cycling life (capacity retention of 94.64% at 1 C after 1000 cycles and 93.98% at 10 C after 5000 cycles). Thus, the Na4Fe3(PO4)2P2O7 material with excellent electrochemical properties, low cost, and a simple synthesis method is a promising cathode electrode for SIBs.