Energy implications, environmental impact, applications, and challenges of metal air batteries

This work highlights the energy implications, environmental impact, applications, and challenges of Metal-Air Batteries (MABs). MABs are classified based on the metal anode that is oxidized in one of its half reactions. The metal anode of choice dictates the energy density of the MAB. It is revealed that MABs bear a significantly higher energy density, compared to all other battery technology alternatives, which can range from 300 Wh/kg for iron-based MABs to 8000 Wh/kg for silicon-based MABs. Additionally, this work discusses the grid-scale potential of MABs and addresses challenges that are manifested in the form of oxygen reduction reaction (ORR) catalysts' deposition and cost. Moreover, a collection of literature that presented life cycle analysis (LCA) on MABs is highlighted to show the environmental impact of these batteries across their various lifetime stages. In some cases, it was noted that scaling up MABs can reduce their energy requirements during the production stage from 246.7 MJ/kg to 19.9 MJ/kg by increasing the number of membranes and cathodes produced. Applications including electric vehicles, GPS tracking devices, hearing-aid devices, as well as mobile military devices were presented. Finally, thermodynamic Oxygen Reduction Reaction (ORR), cost, and infrastructure-related challenges and limitations are discussed to lay the ground for future research and development.