Practical Cathodes for Sodium-Ion Batteries: Who Will Take The Crown?

In recent decades, sodium-ion batteries (SIBs) have received increasing attention because they offer cost and safety advantages and avoid the challenges related to limited lithium/cobalt/nickel resources and environmental pollution. Because the sodium storage performance and production cost of SIBs are dominated by the cathode performance, developing cathode materials with large-scale production capacity is the key to achieving commercial applications of SIBs. Therefore, developing host materials with high energy density, long cycling life, low production cost, and high chemical/environmental stability is crucial for implementing advanced SIBs. Among the developed cathode materials for SIBs, O3-type sodiated transition-metal oxides have attracted extensive attention owing to their simple synthesis methods, high theoretical specific capacity, and sufficient Na content. However, the relatively large Na-ion radius leads to sluggish diffusion kinetics and inevitable complex phase transitions during the deintercalation/intercalation process, resulting in poor rate capability and cycling stability. Therefore, this review comprehensively summarizes the research progress and modification strategies for O3-type cathodes, including the component design, surface modification, and optimization of synthesis methods. This work aims to guide the development of commercial layered oxides and provide technical support for the next generation of energy-storage systems.