Interfacial Engineering of Layered Cathodes for Sodium-Ion Batteries: Strategies, Mechanisms, and Perspectives

Layered transition metal oxides (LTMOs), with a unique two-dimensional framework, are research hotspots for sodium-ion battery (SIB) cathodes due to their high specific capacity, environmental benignity, structural tunability, and facile synthesis, showing great commercial potential for large-scale energy storage. However, their practical application is severely hindered by unique interfacial instability challenges during long-term Na⁺ (de)intercalation. These include interface strain induced by the larger radius of Na⁺ ions, transition metal dissolution, lattice oxygen loss, and interface cracking caused by phase transitions such as P2-O2 or O3-P2. Collectively, these issues lead to drastic capacity fading and poor electrochemical performance. Interfacial engineering is pivotal for regulating electrode-electrolyte interface properties, effectively mitigating side reactions and enhancing LTMOs stability and performance. Representative strategies include surface modification, elemental doping, multiscale structural regulation, and electrolyte/interface engineering approaches, while their practical application is restricted by material-specific limitations, unclear synergistic effects, and scalable fabrication challenges. This review summarizes recent advances in interfacial engineering for LTMOs cathodes, focusing on modification mechanisms of key strategies. It discusses how these approaches address interfacial instability, outlines current challenges, and proposes future directions for synergistic optimization, providing theoretical guidance for high-performance, long-life LTMOs cathodes in SIBs.