Fast Zn 2+ Transport in Aqueous Zinc Ion Batteries: A Composition‐Activity Analysis of Prussian Blue Analogues as Positive and Hydrated Zinc Vanadate as Negative Electrode Materials

ABSTRACT With growing demand for safe and sustainable energy‐storage systems, aqueous zinc‐ion batteries (AZIBs) are emerging as promising candidates due to their non‐flammable electrolytes and environmental benignity. However, their practical deployment is hindered by sluggish Zn 2+ transport and electrode instability. In this work, we examine the influence of composition on Zn 2+ storage in Prussian Blue Analogue (PBA) positive electrodes‐ Na 2 CuFe(CN) 6 ·yH 2 O (Cu‐PBA), Na 2 CoFe(CN) 6 ·yH 2 O (Co‐PBA) and the mixed‐metal Na 2 Co 0.5 Cu 0.5 Fe(CN) 6 ·yH 2 O (CoCu‐PBA). Guided by theoretical calculations, CoCu‐PBA exhibits the most favorable Zn 2+ intercalation behavior, delivering 58 mAh g −1 at 100 mA g −1 . For the negative electrode, Zn‐vanadate (Zn x V 2 O 5 ·yH 2 O, ZnVO) with its expanded ion‐diffusion channels and lower band gap compared to V 2 O 5 , provides enhanced diffusion pathways and achieves 80 mAh g −1 at 100 mA g −1 . A full AZIB cell assembled using CoCu‐PBA and ZnVO with a ZnSO 4– silica gel electrolyte delivers a specific capacity of 49 mAh g −1 (@100 mA g −1 ), an energy density of 61 Wh kg −1 (@125 W kg −1 ), a power density of 612 W kg −1 (@18 Wh kg −1 ) and excellent cycling stability (92% retention over 500 cycles at 300 mA g −1 ). These findings highlight an optimized electrode–electrolyte design for advancing high‐performance AZIBs.