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

• • The amorphous NFPO/rGO composite delivers a specific capacity of 79.1 mAh g−1 after 1000 cycles at 0.1 A g−1, demonstrating exceptional long-term cycling stability critical for grid-scale energy storage applications where electrode longevity directly impacts levelized cost. • • The amorphous phase is essential for electrochemical activity; crystalline NFPO/rGO is electrochemically inactive, underscoring that structural disorder facilitates Na+ transport and redox reactions, a key design principle for next-generation cathodes. • • In-situ XRD reveals a phase transformation from amorphous NaFeP2O7 to triclinic Na2FeP2O7 during first discharge, followed by evolution to a highly disordered structure in subsequent cycles, providing mechanistic insight into the activation process and capacity retention. • • The synthesis leverages industrial jarosite residue (20–40% Fe) as the iron source, addressing environmental pollution from over 60 million tons of accumulated waste while reducing raw material costs for battery manufacturing, aligning with circular economy imperatives.