Sodium storage performance and mechanism of a novel amorphous NaFeP₂O₇/rGO cathode material derived from jarosite residue

The high-value utilization of industrial wastes is critically important for environmental protection and the sustainable development of society. In this work, amorphous NaFeP2O7 (named NFPO) and NaFeP2O7/rGO (named NFPO/rGO) composite are synthesized via a selective chemical precipitation approach, utilizing the industrial jarosite residue as the iron source. The sodium storage performance and mechanism of this amorphous NFPO/rGO composite as a novel cathode material for sodium-ion batteries (SIBs) are explored for the first time. The as-synthesized amorphous NFPO/rGO composite exhibits outstanding long-term cycling performance of 79.1 mAh g−1 after 1000 cycles at 0.1 A g−1, while the crystalline NFPO/rGO composite does not work. Galvanostatic intermittent titration technique and in-situ electrochemical impedance spectroscopy analysis demonstrate that the amorphous NFPO/rGO composite has high Na+ diffusivity and fast kinetics. In-situ X-ray diffraction analysis reveals the structure change from amorphous NaFeP2O7 to triclinic Na2FeP2O7 during the first discharge process and then evolves to a highly disordered structure in the subsequent charge/discharge cycles. The present work not only provides an avenue for the high-value utilization of jarosite residue but also offers theoretical guidance for the structural design and development of NaFeP2O7-based cathode materials for SIBs.