Advancements in improving the thermal stability of oxide cathodes in sodium-ion batteries: fundamental mechanisms, critical challenges and modification approaches

Sodium-ion batteries (SIBs) are an effective complement to lithium-ion batteries (LIBs) due to their resource and cost advantages. The layered oxide cathode of SIBs with high energy and power density, feasible large-scale production, shows promising application in power batteries, start-stop batteries and so on, but is severely hindered by poor thermal stability, which is closely associated with the application safety. Firstly, the structural characteristics and the primary factors that influence the thermal stability are initially focused on. Secondly, the thermal runaway behaviors and corresponding modification strategies are comprehensively reviewed. Lastly, some critical development directions to improve the thermal stability of layered oxide cathodes are discussed. This review has the potential to offer guidance for the development of high-safety layered oxide cathodes.