A High‐Entropy Prussian Blue Analog for Aqueous Potassium‐Ion Batteries

Abstract Aqueous potassium‐ion batteries (AKIBs) are considered promising electrochemical energy storage systems owing to their high safety and cost‐effectiveness. However, the structural degradation resulting from the repeated accommodation of large K‐ions and the dissolution of active electrode materials in highly dielectric aqueous electrolytes often lead to unsatisfactory electrochemical performance. This study introduces a high‐entropy Prussian blue analog (HEPBA) cathode material for AKIBs, demonstrating significantly enhanced structural stability and reduced dissolution. The HEPBA exhibits a highly reversible specific capacity of 102.4 mAh g −1 , with 84.4% capacity retention after undergoing 3448 cycles over a duration of 270 days. Mechanistic insights derived from comprehensive experimental investigations, supported by theoretical calculations, reveal that the HEPBA features a robust structure resistant to dissolution, a solid‐solution reaction pathway with negligible volume variation during charge–discharge, and efficient ion transport kinetics characterized by a reduced band gap and a low energy barrier. This study represents a measurable step forward in the development of long‐lasting electrode materials for aqueous AKIBs.