Enabling high-depth-of-discharge operation of Zn powder anodes via conformal SnO2 coating

Abstract

Aqueous zinc-ion batteries (AZIBs) are gaining attention due to their safety and cost-effectiveness. However, zinc (Zn) anodes face persistent issues such as dendrite growth, side reactions, and the accumulation of inactive Zn, particularly when Zn powder is used due to its high surface area and corrosion susceptibility. In this work, we demonstrate a conformal SnO2 surface engineering strategy that enables slurry casted Zn powder anodes to operate stably under high depth of discharge (DOD) conditions in aqueous Zn-ion batteries. Electrochemical testing revealed enhanced cycling stability and plating/stripping reversibility in SnO2 coated Zn powder, accompanied by suppressed side reactions and reduced inactive Zn formation. Coulombic efficiency (CE) and DOD were significantly improved, while electrochemical impedance spectroscopy (EIS) confirmed reduced charge transfer resistance and improved interfacial characteristics. The coated Zn powder anodes also exhibited strong compatibility with zinc vanadium oxide (ZVO) and manganese dioxide (β-MnO2) cathodes, demonstrating their versatility. Their performance in pouch cell configurations suggests practical scalability. Overall, this study highlights SnO2 surface coating as an effective strategy for improving Zn powder anode reversibility and durability, offering a feasible path toward high-performance and long-lasting AZIBs.