Entropy Engineering and Multi-Metal Synergy Stabilize Prussian Blue Analogue Cathodes for Long-Life Aqueous Zinc-Ion Batteries

Abstract Prussian blue analogues (PBAs), owing to their distinctive three-dimensional open framework structures featuring wide ion channels and excellent structural tunability, have drawn increasing attention as promising cathode materials for aqueous zinc-ion batteries (AZIBs). However, their electrochemical cycling stability is often hindered by the dissolution of transition-metal ions and structural degradation induced by intrinsic defects and coordinated water molecules. To address these limitations, a high-entropy Prussian blue analogue (HE-PBA) cathode material was synthesized by incorporating five transition metals (Mn, Co, Ni, Zn, and Cu) into the M1 sites. The resulting material demonstrates a reduced defects density and a lower level of coordinated water (K1.68(Mn0.22Co0.20Ni0.19Zn0.20Cu0.19)[Fe(CN)6]0.96□0.04·0.37H2O). Electrochemical tests reveal that the entropy-driven “cocktail effect” synergistically stabilizes the crystal framework and facilitates rapid Zn2+ diffusion. The M5HCF cathode delivers outstanding long-term cycling stability, retaining 62 mAh g–1 after 10,000 cycles, with an ultralow capacity decay of 0.0016% per cycle, and excellent rate capability (69 mAh g–1 at 5 A g–1). Ex situ XPS tracks the dynamic evolution of M–N vs Fe–C redox contributions during cycling, clarifying the origin of the gradual plateau changes. These findings offer a practical strategy for durable AZIB cathodes.