Tuning Fe ²⁺ Release Kinetics via Coordination Engineering Toward Highly Stable Prussian Blue Analogs with Enhanced K ⁺ Storage

Abstract Prussian blue analogs (PBAs) are promising cathode materials for potassium‐ion batteries (PIBs) due to their low cost and open framework that facilitates rapid ion transport. However, severe performance degradation upon cycling arises from structural defects that impedes the practical implementation of PBAs‐based PIBs. Herein, a dual‐chelating agent co‐precipitation strategy is proposed to synthesize potassium‐rich PBAs. By modulating the potassium citrate (KCA) to dipotassium ethylenediaminetetraacetate (EDTA‐2K) ratio, the strategy precisely controls the coordination environment during co‐precipitation, regulates Fe 2+ release kinetics, and ultimately yields K 1.7 Fe[Fe(CN) 6 ] 0.83 ·◻ 0.17 ·0.73H 2 O (KCA75) material with high reversible potassium content (1.7 mol −1 ) and low coordinated water content (4.7 wt.%). In situ Raman analysis demonstrates that the controlled Fe 2+ release kinetics effectively suppress the formation of [Fe(CN) 6 ] 4− vacancies and minimize water incorporation. Consequently, the optimized KCA75 cathode delivers a reversible capacity of 128 mAh g −1 at 0.2C, exceptional rate capability (65 mAh g −1 even at 10C), and extended cycling stability (94.8% capacity retention ratio after 1000 cycles at 5C). The KCA75//graphite full cell demonstrates remarkable cycling stability, maintaining 92.7% capacity retention over 1 000 cycles. These findings underscore the potential of PBAs as PIBs cathodes and highlight the critical role of Fe 2+ release kinetics regulation through coordination engineering in optimizing PBAs structural integrity.