Multi‐Dimensional Characterization of Sodium‐Ion Battery Materials: Bridging Atomic Structure, Interface Chemistry and Electrochemical Performance

ABSTRACT Sodium‐ion batteries (SIBs) have emerged as promising candidates for large‐scale energy storage due to their cost‐effectiveness and resource abundance. However, challenges such as sluggish ion diffusion kinetics, structural degradation, and interfacial instability hinder their practical applications. This review systematically summarizes recent advancements in multi‐dimensional characterization techniques for SIBs, covering atomic‐scale crystal structure evolution, compositional distribution, microstructural dynamics, and chemical state changes. We highlight the critical role of in situ and ex situ techniques (e.g., X‐ray diffraction [XRD], transmission electron microscopy [TEM], X‐ray photoelectron spectroscopy [XPS], X‐ray absorption spectroscopy [XAS]) in elucidating structure‐property relationships, particularly in multi‐element doping, composite materials, and novel electrolyte systems. Key findings include: (1) multi‐element doping strategies mitigate phase transition stresses as revealed by in situ XRD and atomic‐scale strain mapping; (2) interface engineering (e.g., SEI/CEI optimization) enhances cycling stability characterized by XPS and TEM; and (3) synchrotron‐based methods (e.g., XAS) reveal dynamic redox mechanisms. Finally, we discuss future opportunities in ultra‐resolution imaging, AI‐driven analysis, and extreme‐condition characterization to accelerate the development of high‐performance SIBs.