Reactive Oxygen Species Resistive Redox Mediator in Lithium–Oxygen Batteries

Abstract

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.