Effect of Microstructure on the Performance of a Zn-Al Alloy Anode for Zn-Air Battery Application

Zn-air batteries utilizing Zn-Al alloy anodes are well-known to possess higher specific capacities and open-circuit voltages (OCVs) than those using pure Zn anodes. In this study, the effect of microstructure on the anodic performance of a Zn-22wt%Al alloy was investigated using both cell discharge and volumetric hydrogen evolution tests. Three unique microstructures (i.e. fine equiaxed, coarse equiaxed, and lamellar) achieved via specific heat treatments, were included in the evaluation. The resulting discharge voltage, specific capacity, and OCV were found to be independent of the alloy microstructure, while the hydrogen evolution rate of the alloy anode was significantly influenced by the heat-treatment procedure. The alloy sample with the coarse equiaxed microstructure had the lowest hydrogen evolution rate. This microstructure was formed by water quenching the annealed sample and then heat treating it at 260 degrees C for 12 h. Although the reduction in the corrosion rate of the alloy was not enough to cause it to have immediate use, this result does point out the potential of further improvement via microstructural manipulation. (c) 2012 The Electrochemical Society. All rights reserved.