Structural stability of layered oxides for sodium-ion batteries: Insights and strategies

Sodium-ion batteries have garnered significant attention due to the notable advantages in resource availability and cost-effectiveness, offering an alternative solution to lithium-ion batteries. Layered oxide cathodes (LOCs), a key component of SIBs, are among the most commercially viable materials due to their low cost, ease of synthesis, and high theoretical capacity. However, challenges such as lattice defects and particle cracking caused by air exposure and electrochemical cycling lead to structural instability, resulting in capacity degradation and reduced cycle life. Addressing these issues requires multi-scale investigations, from atomic to macroscopic levels, to fully understand structural evolution. This review investigates the intrinsic mechanisms governing the structural stability of LOCs and discusses strategies for integrating multi-scale information, from atomic structure and material properties to electrochemical performance, to bridge theoretical and experimental research. Furthermore, we discuss effective approaches to enhance structural stability and outline future research directions to accelerate SIB commercialization and advance their role in energy storage.