Leveraging Entropy and Crystal Structure Engineering in Prussian Blue Analogue Cathodes for Advancing Sodium-Ion Batteries

The synergistic engineering of chemical complexity and crystal structures has been applied to Prussian blue analogue (PBA) cathodes in this work. More precisely, the high-entropy concept has been successfully introduced into two structure types of identical composition, namely, cubic and monoclinic. Through the utilization of a variety of complementary characterization techniques, a comprehensive investigation into the electrochemical behavior of the cubic and monoclinic PBAs has been conducted, providing nuanced insights. The implementation of the high-entropy concept exhibits crucial selectivity toward the intrinsic crystal structure. Specifically, while the overall cycling stability of both cathode systems is significantly improved, the synergistic interplay of crystal structure engineering and entropy proves particularly significant. After optimization, the cubic PBA demonstrates structural advantages, showcasing good reversibility, minimal capacity loss, high thermal stability, and unparalleled endurance even under harsh conditions (high specific current and temperature).