Whispers of Entropic Distortion Elevating Voltage and Electrochemical Depth in Potassium Hexacyanoferrate Cathodes

Abstract Prussian Blue Analogues (PBAs) are regarded as one of the most promising cathode materials for potassium‐ion batteries (PIBs) due to their broad operating voltage range, low potassium‐ion diffusion barriers, and cost‐effective, simple synthesis. However, the passivation of low‐spin transition metal centers and inherently poor electronic conductivity severely limit PBAs' potential to achieve high energy density and long‐term cycling stability. In this study, the first successful activation of low‐spin transition metal reactivity in a non‐aqueous PIB system through the incorporation of a high‐entropy multimetallic coordination strategy is reported. This approach not only precisely regulates the voltage platform but also significantly enhances the material's energy density. The synthesized high‐entropy K 1.19 Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2 Mn 0.2 [Fe(CN) 6 ] 0.79 □ 0.21 ·1.16H 2 O (HEPBA) cathode achieved a remarkable energy density of 407.67 W h kg −1 at an average working voltage of 3.89 V, with a capacity retention of 88.03% after 2000 cycles at 500 mA g −1 . Density functional theory (DFT) and field emission analysis (FEA) calculations revealed that the high‐entropy design not only improved the electronic conductivity during K + intercalation but also significantly reduced ion diffusion barriers. Additionally, the material exhibited reduced volumetric expansion during potassium‐ion insertion/extraction, greatly enhancing its long‐term cycling stability.