A Universal Precipitation‐Transformation Strategy Toward Low‐Defect Prussian Blue Analogs for High‐Performance Sodium‐Ion Batteries

Prussian blue analogs (PBAs) are considered promising cathode materials for sodium‐ion batteries (SIBs) due to their low cost and open framework structure. However, their practical application is hindered by intrinsic [Fe(CN) 6 ] 4− vacancies and coordinated water, which degrade electrochemical performance, alongside challenges in scalable and cost‐effective synthesis. Herein, we report a universal precipitation‐transformation strategy that utilizes insoluble metal compounds as precursors to synthesize highly crystalline PBAs. This approach leverages the slow dissolution‐precipitation equilibrium of low‐solubility precursors to precisely control metal ion release, fundamentally retarding nucleation and crystal growth kinetics. The strategy demonstrates excellent versatility, enabling the synthesis of single‐metal, binary‐metal, multi‐metal, and even high‐entropy PBAs with monoclinic or cubic structures, and is readily scalable to 596‐gram‐level production. As a SIB cathode, the optimized Fe‐based PBA (T‐FeHCF) exhibits a high specific capacity of 150.5 mAh g −1 at 0.1 C, excellent rate capability (73.6 mAh g −1 at 20 C), and outstanding cycling stability with 93% capacity retention after 2000 cycles at 5 C. Full‐cells assembled with hard carbon anodes further demonstrate practical viability, maintaining over 85% capacity retention after 400 cycles. This cost‐effective and environmentally benign synthesis platform provides a viable pathway toward the commercialization of high‐performance PBA cathodes for sustainable energy storage.