Influence of heat treatment on the discharge performance of Mg-Al and Mg-Zn alloys as anodes for the Mg-air battery

This work investigated the use of heat treatment to improve the battery performance of cast Mg-6Zn and Mg-8Al anodes for primary Mg-air batteries. The reason for anodic efficiency drop was quantitively analyzed. Anodes after heat treatment had a discharge voltage that was higher and more-stable than that of cast anodes, attributed to a higher open circuit voltage and smoother exfoliation of discharge products. The solution heat-treated Mg6Zn had the best discharge capacity of 1185 mAh g(-1) and an anodic efficiency of 56 % at 40 mA cm(-2), compared with 928 mAh g(-1) and 44 % for as-cast Mg-6Zn at the same current density. The T6 treated (solution and annealing) Mg-8Al anodes produced the best discharge capacity of 1418 mAh g(-1) and anodic efficiency (at 40 mA cm(-2)) of 63 %. Heat treatment also enhanced the peak energy density from 926 mWh g(-1) (2.5 mA cm(-2)) to 1463 mWh g(-1) (at 10 mA cm(-2) after solution treatment) for Mg-6Zn and from 1501 mWh g(-1) (20 mA cm(-2)) to 1736 mWh g(-1) (at 20 mA cm(-2) after the T6 heat treatment) for Mg-8Al. These improvements were caused by suppressing the anodic hydrogen reaction and dissolving harmful large-sized precipitates. Heat treatment should be considered essential in the production of high-performance anodes for Mg-air batteries.

Automated summary

This study investigated the use of heat treatment to improve the battery performance of cast Mg-6Zn and Mg-8Al anodes for primary Mg-air batteries. The results showed that heat-treated anodes had higher discharge voltage and smoother exfoliation of discharge products, leading to improved discharge capacity and anodic efficiency. Heat treatment also suppressed the anodic hydrogen reaction and dissolved harmful large-sized precipitates.