Three‐Dimensional Holey Graphene Modified Na4Fe3(PO4)2(P2O7)/C as a High‐Performance Cathode for Rechargeable Sodium‐Ion Batteries

Polyanion-type Na₄ Fe₃ (PO₄ )₂ (P₂ O₇ ) (NFPP) is a promising cathode material for sodium-ion batteries due to its low cost and high safety. Herein, a three-dimensional (3D) holey graphene (HG) modified NFPP/C material (NFPPCHG) has been successfully prepared by a simple and scalable ball milling strategy with sodium phytate and ferrous oxalate as precursors. The introduction of HG can obviously improve the specific surface area, electronic conductivity, and ions transport performance of NFPPCHG and largely enhance its electrochemical properties. The prepared NFPPCHG delivers a high reversible capacity of 118 mAh g^-1 at 0.2 C and keeps a considerable capacity of 53 mAh g^-1 even at an ultrahigh rate of 100 C. NFPPCHG also shows excellent performance at 55 °C and -20 °C. Moreover, in situ distribution of relaxation time analysis further demonstrates NFPPCHG has superior electrochemical kinetics. In addition, the HC//NFPPCHG full cell displays good performance, suggesting great potential of the prepared material for practical applications.