Interfacial Dipole Reorganization Enables Ultrafast Sodium Storage in Na <sub>4</sub> Fe <sub>3</sub> (PO <sub>4</sub> ) <sub>2</sub> P
As a promising cathode material for large‐scale sodium‐ion energy storage, Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) still suffers from sluggish Na + kinetics and insufficient electronic conductivity. Herein, we propose a bulk‐to‐interface coupling framework in which substitution‐induced electronic regulatio...