Degradation Mecha-nisms and Mitigation Strategies for High-Voltage Layered Ox-ide Cathodes for So-dium-Ion Batteries

Abstract

Sodium-ion batteries (SIBs) are increasingly recognized as promising candidates for large-scale energy storage owing to the natural abundance and low cost of sodium resources. Among various cathode materials, high-voltage layered oxide cathodes have attracted considerable attention due to high energy density, environmental friendliness, and scalable synthesis. However, operation at elevated voltages unavoidably gives rise to a series of complex degradation phenomena, including bulk structural instability induced by transition-metal migration and dissolution, irreversible lattice oxygen release, and aggravated interfacial parasitic reactions at the electrode/electrolyte interface. These severely compromise the structural integrity, electrochemical reversibility, and long-term cycling stability of high-voltage layered oxide cathodes, thereby limiting their practical application. In this review, a comprehensive overview of the degradation mechanisms of high-voltage layered oxide cathodes in SIBs is presented, encompassing bulk crystal structure evolution as well as surface and interfacial reactions under high-voltage operation. Recent advances in mitigation strategies, including elemental doping, structural and compositional engineering, and interface and surface modification, are systematically summarized and critically discussed, followed by a brief analysis of their practical economic implications. Finally, key challenges and future perspectives are outlined to provide insights into the rational design of high-energy-density and long-cycle-life sodium-ion batteries.