Dual Ionic–Electronic Conduction Engineering Unlocks High‐Rate Kinetics in Long‐Cycling Na ₄ Fe ₃ (PO ₄ ) ₂ P ₂ O ₇ Cathodes

ABSTRACT Na ₄ Fe ₃ (PO ₄ ) ₂ P ₂ O ₇ (NFPP) holds great potential as a promising cathode material for sodium‐ion batteries. However, its practical viability remains severely constrained by the formation of electrochemically inactive maricite–NaFePO ₄ during synthesis, low inherent conductivity, and intrinsically sluggish Na ⁺ transport. Herein, we present a cathode featuring a cheese‐like porous framework, which effectively overcomes existing limitations, enabling highly efficient dual ionic–electronic conduction. The interconnected porous architecture dramatically shortens Na ⁺ diffusion pathways and facilitates rapid electrolyte infiltration, thereby accelerating ion‐transport kinetics, while the mechanically resilient block morphology efficiently buffers the substantial volume fluctuations during charge–discharge cycling. Concurrently, the incorporation of Cr ³⁺ markedly accelerates charge‐transfer kinetics while effectively suppressing electrostatic repulsion during (de)sodiation, resulting in a reduced Na ⁺ migration barrier and the activation of Na3 sites. Consequently, this design enables a highly reversible capacity of 117.9 mAh g ⁻¹ at 0.1C together with exceptional long‐term stability, retaining 90.7% capacity after 3000 cycles at 20C. This study establishes a powerful structural‐engineering paradigm for the rational design and modification of high‐performance sodium‐ion cathode materials.