Multiscale Characterization of Intrinsic Defects in Prussian White Cathodes: Bridging Defect Chemistry with Structure and Electrochemical Performance

Prussian White (PW) is a highly promising cathode material for sodium‐ and potassium‐ion batteries. However, its typical co‐precipitation synthesis inevitably introduces intrinsic structural defects—most notably [Fe(CN)6] vacancies (VFeCN)—which critically undermine electrochemical performance. Given the thermodynamic and kinetic inevitability of these vacancies, merely suppressing their formation is insufficient. Instead, a deep understanding of their formation mechanisms, structural roles, and degradation pathways is essential for performance optimization. This review systematically deconstructs the types and origins of intrinsic vacancies in PW—including VFeCN, transition metal vacancies (VTM), and cyanide ligand vacancies (VCN)—with a particular emphasis on the conditions that govern VFeCN generation. More importantly, it establishes a multidimensional, multiscale defect characterization framework, spanning electronic structure, atomic coordination, crystal order, and mesoscale morphology. Beyond characterization, the review correlates vacancy chemistry with key electrochemical consequences. VFeCN defects reduce alkali‐ion storage sites, disrupt continuous ion transport pathways, and trigger interfacial side reactions—collectively leading to capacity fading, rate deterioration, limited cycling life, poor low‐temperature performance, and thermal instability. By bridging intrinsic defect chemistry with macroscopic electrochemical performance, this review provides a strategic roadmap for defect‐informed design of robust and high‐efficiency PW cathodes.