Reactive Oxygen Species Resistive Redox Mediator in Lithium-Oxygen Batteries

The utilization of redox mediators (RMs) in lithium-oxygen batteries (LOBs) has underscored their utility in high overpotential during the charging process. Among the currently known RMs, it is exceptionally challenging to identify those with a redox potential capable of attenuating singlet oxygen (¹O₂) generation while resisting degradation by reactive oxygen species (ROS), such as ¹O₂ and superoxide (O₂ ^•-). In this context, computational and experimental approaches for rational molecular design have led to the development of 7,7'-bi-7-azabicyclo[2.2.1]heptane (BAC), a newly suggested RM incorporating N-N interconnected aza-bicycles. BAC harnesses the advantages of falling within the potential range that suppresses ¹O₂ generation, as previously reported N-N embedded non-bicyclic RMs, and effectively defends against ROS-induced degradation due to the incorporation of a novel bicyclic moiety. Unlike the non-bicyclic RMs, which exhibit reduced 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. This study introduces a precise and rational design strategy for low-molecular-weight RMs, marking a significant step forward in advancing LOB development by improving efficiency, stability, and practical applicability.