Advancing Sodium-Ion Battery Performance: Innovative Doping and Coating Strategies for Layered Oxide Cathode Materials

The integration of intermittent renewable energy sources, such as wind and solar power, requires efficient large-scale energy storage systems. Sodium-ion batteries (SIBs) have garnered attention for grid-scale applications due to their cost-effectiveness and long cycle life. Among various cathode materials, layered oxides stand out for their tunable Na content, environmental compatibility, and safety. However, their practical deployment faces challenges, including structural instability caused by phase transitions, Na⁺/vacancy ordering, and surface degradation, leading to capacity decay. To address these issues, doping and coating strategies are extensively explored to enhance structural stability, improve Na⁺ diffusion, and mitigate electrode-electrolyte side reactions. This review critically analyzes recent advancements in these modification approaches, revealing their underlying mechanisms and their effects on electrochemical performance. Additionally, emerging strategies, such as multi-element synergistic doping and doping-coating dual engineering, are highlighted for further optimizing electrochemical properties. These insights provide a foundation for the rational design of next-generation layered oxide cathodes, accelerating the commercialization of SIBs for sustainable energy storage.