ROS-Resistant Redox Mediator in Lithium-Oxygen Batteries

Abstract The utilization of redox mediators (RMs) in lithium-oxygen batteries (LOBs) have underscored their utility in addressing the challenge of the elevated overpotential during the charging process. Nonetheless, the generation of highly electrophilic singlet oxygen (1O2) throughout the battery cycles leads to adverse reactions with RMs, thereby impeding their effectiveness. In the quest for enhanced RM durability, this study unveils a novel RM, 7,7'-bi-7-azabicyclo[2.2.1]heptane (BAC), incorporating N–N interconnected aza-bicycles, and assesses its efficacy and robustness relative to those of other N–N non-bicyclic RMs. Unlike non-bicyclic RMs, which exhibit diminished O2 evolution after exposure to 1O2, BAC maintains consistent O2 profiles during charging, indicating its superior 1O2 resistance and steady redox-catalyst performance in LOBs. Theoretical analyses align with the experimental findings that the bicyclic structural design of BAC confers a superior ability to resist oxidative degradation through cleavage of the C–H bonds adjacent to nitrogen atoms.