Understanding How Structure Influences Electrochemical Behavior When ZnO Is Used to Suppress Aluminum Corrosion in Alkaline Electrolytes

Abstract

The severe corrosion rate of aluminum (Al), coupled with hydrogen evolution (H2 gassing), is the major roadblock preventing the widespread deployment of Al as the anode material in primary and secondary alkaline batteries. One of the most successful approaches to reduce this corrosion has been the addition of ZnO to the alkaline KOH electrolyte, which results in the spontaneous electroless deposition of a protective metallic Zn film on the Al surface. However, the fundamental structural and electrochemical characterization of Zn on Al as well as the influence of ZnO/KOH composition need to be investigated. This study aims to develop a novel fundamental understanding of the protection mechanism against Al corrosion when zincate (from dissolved ZnO) is added to KOH electrolytes. The effects of both ZnO concentration and KOH concentration are probed. Morphological studies of the spontaneous Zn film were realized using SEM, XRD, N2 adsorption and measurements of real time H2 gas evolution. These were coupled with discharge experiments to create a new structure-function understanding for ZnO protection of Al. It should be noted that electrolytes enabling protective Zn films with good adherence and density were found, and capacities near the Al theoretical capacity were achieved.