D-band center modulation of Prussian blue analogues through a high-entropy strategy for aqueous potassium-ion batteries

Abstract

Prussian blue analogues (PBAs) have recently emerged as promising candidates for aqueous potassium-ion batteries (APIBs), and their potential is attributed to high energy density and low cost. However, PBAs still face challenges such as structural instability and transition metal dissolution during cycling, resulting in a poor cycle life. Herein, a high-entropy strategy is employed to enhance the cycling stability of Fe-based PBAs by elevating the d-band center of Fe atoms. This regulation enables the hybridization of 3d energy levels, thereby strengthening the Fe–N bond and optimizing the electronic structure. In situ/ex situ techniques, combined with density functional theory calculations, demonstrate that high-entropy Fe-based PBAs (HEFeHCF) exhibit a solid-solution reaction with minimal volume change and a low K⁺ diffusion barrier. As a result, HEFeHCF achieves a remarkable capacity retention of 85.9% over 10 000 cycles at a high current density of 5 A g⁻¹. Furthermore, when coupled with an organic anode, the full cell retains 84.5% capacity after 10 000 cycles. This work offers a new optimization approach at the electronic level for PBAs through a high-entropy strategy in aqueous batteries.