Selective lithium extraction and Fe–P component reconstruction toward high-performance Na4Fe3(PO4)2P2O7 as cathode materials of sodium ion batteries

Na-insertion and carbon coating. The regenerated cathode delivers 99.74% capacity retention (400 cycles, 1C) and 97.23% retention after 600 cycles (5C), demonstrating superior cyclability for sustainable battery recycling and low-cost energy storage.