Advanced cathode engineering in sodium-ion batteries: doping, phase, and interface modulation from layer oxides to polyanionics

Abstract Sodium-ion batteries (SIBs) have attracted significant attention as viable alternatives to lithium-ion batteries; however, their practical advancement remains limited by cathode-related challenges, including sluggish Na + diffusion, structural degradation, and rapid capacity decay at high rates. This review highlights recent progress in cathode engineering strategies aimed at overcoming these limitations. Advanced approaches, including high-entropy design, multiphase construction, surface modification, defect regulation, and multi-element doping, have been explored to enhance structural integrity, charge-transfer kinetics, and cycling stability. High-entropy and multicomponent systems effectively mitigate phase transitions and improve thermal/electrochemical stability, while multiphase architectures facilitate Na + transport and reversible capacity retention. Surface engineering through functional coatings and interface modification stabilizes electrode–electrolyte interactions, whereas defect engineering, particularly oxygen vacancy modulation, optimizes electronic structures and ion migration pathways. Furthermore, cationic, anionic, and co-doping strategies have significantly improved the conductivity, redox activity, and structural durability of polyanionic cathodes. These emerging engineering approaches provide promising pathways toward the development of high-performance and durable cathode materials for next-generation SIBs.