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.