Bridging fundamental mechanisms and scalable manufacturing of Na4Fe3(PO4)2P2O7 for large-scale sodium-ion storage

Abstract

Sodium-ion batteries have emerged as promising candidates for large-scale energy storage systems, where the cost and long-term stability of cathode materials are of paramount importance. Among various candidates, the open-frame-structured Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) cathode stands out due to the ultra-low cost of its iron-based raw materials, exceptional cycling longevity, remarkable safety, and environmental friendliness. This perspective provides a comprehensive exploration of the structure–property relationship of NFPP, electrochemical optimization strategies, and pathways toward industrialization. Although its gravimetric energy density is relatively modest, NFPP exhibits significant advantages in terms of raw material cost, cycle life, rate capability, and operational stability over a wide temperature range. We delve into the mechanisms for enhancing its intrinsic electronic conductivity and ion diffusion kinetics via defect engineering, morphology control, and heterostructure design. Furthermore, this work systematically evaluates scalable production approaches and discusses key techniques for improving electrode compaction density, controlling particle size distribution, and ensuring phase purity. Finally, we outline the challenges and opportunities for NFPP in advancing the commercialization of sodium-ion batteries as the next-generation energy storage systems with low cost and long cycle life.