Na4Fe3(PO4)2(P2O7) cathodes for sodium-ion batteries: Modification strategies and practical prospects

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Owing to the availability and low cost of sodium, sodium-ion batteries (SIBs) are regarded as an attractive substitute for lithium-ion batteries (LIBs) for large-scale energy storage. Non-toxic, cost-effective Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) has gained substantial attention as a viable cathode material, offering a stable three-dimensional framework, reversible (de)sodiation behavior, and high structural stability. However, its practical use is limited by poor electronic conductivity, slow Na⁺ diffusion, and volume changes during cycling. To provide targeted theoretical support and technical references for the commercialization of NFPP materials, a systematic and comprehensive understanding of its modification strategies and corresponding intrinsic reaction mechanisms is needed. This review summarizes recent advances in and future prospects for NFPP as a commercial-grade cathode material for SIBs. First, we summarize research progress on key modification strategies, including carbon modification, defect engineering, ion doping, structural compositing, and interface modulation, in relation to the corresponding sodium storage mechanisms. Second, we identify the key gaps between the current laboratory research and the practical commercial application of NFPP. The paper concludes by discussing the future prospects and potential research directions for NFPP cathodes in SIBs, providing valuable insights into the practical optimization of NFPP cathodes to address challenges for their industrial application.