Influence of Mo and Co Incorporation on Electrochemical Kinetics and Sodium-Storage Behavior of Prussian Blue Analogue Cathodes

Abstract

Prussian blue analogues (PBAs) are promising cathode materials for sodium-ion batteries; however, their electrochemical performance is often limited by sluggish charge-transfer kinetics and poor electronic conductivity. In this work, the influence of Mo and Co incorporation on the electrochemical kinetics and sodium-storage mechanism of PBA cathodes was systematically investigated using temperature-dependent electrochemical impedance spectroscopy, Arrhenius analysis, exchange current density calculations, cyclic voltammetry, and Dunn analysis. Co-PBA exhibited diffusion-dominated sodium storage with the highest charge-transfer resistance, the largest activation energy$(E_{CT}^{\#}=23.102\mathrm{kJ}{\mathrm{mol}}^{-1})$⁠, and the lowest exchange current density. In contrast, Mo incorporation significantly improved the electrochemical response by lowering activation barriers and promoting surface-controlled charge-storage processes. Among the investigated materials, MoCo-PBA exhibited the most balanced electrochemical performance, combining the lowest charge-transfer activation energy $(E_{CT}^{\#}=12.39\mathrm{kJ}{\mathrm{mol}}^{-1})$⁠, efficient interfacial charge transfer, improved reversibility, and mixed diffusion/pseudocapacitive charge storage. BET analysis further revealed the highest specific surface area for MoCo-PBA, contributing to enhanced electrolyte accessibility. These findings demonstrate that simultaneous incorporation of Mo and Co effectively balances interfacial charge-transfer processes and Na⁺ transport within the PBA framework, providing a promising strategy for the development of high-performance sodium-ion battery cathodes.