From Lithium-Oxygen to Lithium-Air Batteries: Challenges and Opportunities

Lithium-air batteries have become a focus of research on future battery technologies. Technical issues associated with lithium-air batteries, however, are rather complex. Apart from the sluggish oxygen reaction kinetics which demand efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts, issues are also inherited from the nature of an open battery system and the use of reactive metal lithium as anode. Lithium-air batteries, which exchange oxygen directly with ambient air, face more challenges due to the additional oxidative agents of moisture, carbon dioxide, etc. which degrade the metal lithium anode, deteriorating the performance of the batteries. In order to improve the cycling performance one must hold a full picture of lithium-oxygen electrochemistry in the presence of carbon dioxide and/or moisture and fully understand the fundamentals of chemistry reactions therein. Recent advances in the exploration of the effect of moisture and CO2 contaminants on Li-O-2 batteries are reviewed, and the mechanistic understanding of discharge/charge process in O-2 at controlled level of moisture and/or CO2 are illustrated. Prospects for development opportunities of Li-air batteries, insight into future research directions, and guidelines for the further development of rechargeable Li-air batteries are also given.