In-situ Construction of Medium-Entropy Interface on Manganese-based Prussian Blue Analogues for Aqueous Zinc-ion Batteries

Abstract

Manganese-based Prussian Blue Analogues (MnPBA) are regarded as highly promising cathode materials for aqueous zinc-ion batteries due to their high energy density. However, their application is hindered by poor intrinsic conductivity and severe Mn dissolution, resulting in inferior rate performance and cycling stability. To address these challenges, this study employs a “cocktail-style” ion exchange strategy to in-situ construct a mid-entropy interface layer (denoted as MnPBA@MEI) on the MnPBA surface, which possesses both thermodynamic stability and superior kinetics. Utilizing the thermodynamic stabilization effect derived from high configurational entropy, this strategy enhances the structural stability of MnPBA while preserving the high capacity output of the bulk material. Simultaneously, the mid-entropy interface layer reduces the desolvation energy barrier of hydrated zinc ions, thereby improving the electrochemical reaction kinetics at the interface. Consequently, the optimized MnPBA@MEI cathode exhibits a high specific capacity of 133 mAh/g. It delivers a capacity of 76 mAh/g even at a high current density of 2 A/g and maintains a reversible capacity of 65 mAh/g after 1000 cycles. In contrast, the pristine MnPBA displays a specific capacity of only 75 mAh/g and fails completely after 600 cycles at 2 A/g. This work achieves a synergistic enhancement of structural stability and kinetics in aqueous battery cathodes via surface entropy engineering, offering a new design paradigm for high-performance aqueous battery cathodes.