Inhibiting Phase Transitions of Prussian Blue Analogs with High-Entropy Strategy for Ultralong-Life Sodium-Ion Battery Cathodes

Abstract

Prussian blue analogs (PBAs) have garnered considerable attention due to open 3D framework and high theoretical capacity. However, unfavorable phase transitions and inherent low conductivity lead to severe capacity decay and poor rate performance. Herein, the high-entropy (HE) concept is incorporated into PBAs to improve their electrochemical properties. By introducing four inert elements sharing N coordination site with Fe, the high-entropy Na_x(FeCuNiMgZn)[Fe(CN)₆] (HEPBA) is constructed. The developed high-entropy Prussian blue analog (HEPBA) exhibits high specific capacity with cyclic stability, stable operation 2000 cycles at 1C, and superior rate performance. Experimental results and theoretical calculations demonstrate that this high-entropy design not only effectively inhibits phase transitions and reinforces structural stability but also activates the redox activity of low-spin-state Fe centers. Simultaneously, it can improve sodium-ion diffusion by optimizing pathways and reducing energy barriers, ultimately enhancing overall performance. This strategy provides an innovative perspective that synergistically optimizes specific capacity, structural stability, and rate performance in PBAs.