Research Progress of Prussian Blue Analogues and Analysis of Their Commercialization Limitations

The concept of sodium‐ion batteries (SIBs) has become a viable choice over the use of lithium‐ion batteries because of the large, available, and economical sodium resources. The three major cathode families for SIBs include layered transition‐metal oxides, polyanionic compounds, and Prussian blue analogues (PBAs), among which PBAs are widely studied because of their open framework, abundant redox sites, and low cost. Nevertheless, their practical electrochemical performance is often lower than theoretical expectations because inherent [Fe(CN) 6 ] vacancies and excess crystal water are introduced during synthesis. These structural flaws negatively impact Na + diffusion, structural reversibility, and cycling stability. This review is a systematic analysis of how vacancies and crystal water affect PBA performance, and summarizes the recent developments in crystal chemistry mechanisms, synthetic methods as well as multi‐scale modification, advanced characterization, and theoretical simulations. The advantages and disadvantages of existing modification technologies are appraised and the main research gaps in quantifying defects, unified modeling, full‐cell configuration, and industrial application are pointed out. Moreover, several future research plans are given, including machine‐learning‐based material optimization, high‐entropy PBA design, and integration with all‐solid‐state batteries.