Iron-Based Phosphate Cathode Materials for Sodium-Ion Batteries: Advances, Challenges, and Future Perspectives

Abstract

Iron-based phosphate sodium-ion batteries (SIBs) have emerged as viable alternatives to lithium-ion batteries (LIBs) for grid-scale energy storage, owing to their high performance, exceptional low-temperature stability, and abundant resources This review systematically evaluates iron-based phosphate cathodes for sodium-ion batteries (SIBs), revealing performance trade-offs and optimization pathways for NaFeO4, Na3Fe2(PO4)3, Na2FePO4F, and Na4Fe3(PO4)2P2O7 (NFPP). NaFeO4 balances ion transport efficiency and stability, while Na3Fe2(PO4)3 offers excellent cyclability but limited capacity. Na2FePO4F and NFPP feature robust structures but face electronic conductivity challenges. NFPP shows promise due to its scalable synthesis and cost efficiency, positioning it as a frontrunner for industrial adoption. Through comprehensive analysis, we propose three strategic research priorities for NFPP: multi-electron redox activation, size-gradient particle design, and electronic structure modulation. These strategies aim to enhance ionic mobility and electronic conductivity, advancing NFPP for scale applications. This review establishes fundamental guidelines for material design while providing strategic insights for next-generation energy storage.

Keywords: iron-based phosphate, sodium-ion batteries, cathodes, ion transport, scale applications