Photoelectrochemistry of oxygen in rechargeable Li-O2 batteries

Rechargeable lithium-oxygen (Li-O-2) batteries are promising energy storage devices due to their high theoretical energy density. However, the sluggish kinetics of the oxygen reduction and evolution reactions (ORR/OER) at the cathodes results in large polarization and low energy efficiency. Although advances have been achieved in electrode material designs and battery configurations, large discharge/charge voltage gaps remain. The introduction of light into Li-O-2 batteries has been demonstrated to boost the reaction kinetics of the ORR/OER, leading to enhanced electrochemical performances, but the understanding of the photoelectrochemical process at oxygen cathodes is limited. This tutorial review focuses on the recent findings regarding photoinvolved oxygen cathodes, battery configurations, and the stability of Li-O-2 batteries, aiming to provide a fundamental understanding of photoinvolved Li-O-2 batteries. The challenges and perspectives are discussed in light of the interdisciplinary nature of photochemistry, materials chemistry, electrochemistry, computation, spectroscopy, and surface science.