Ambilaterality of RM towards 1O2 in Li-O2 Batteries: Trap and Quencher

Lithium oxygen batteries (LOBs) are considered promising next-generation lithium batteries owing to their high theoretical specific energy density. However, several issues must be addressed for realizing the practical applications of LOBs. Among them, the evolution of singlet oxygen (1O2)—which undergoes vigorous reactions that compromise the stability of the system—is a key challenge. The high overpotential induced by low-conductivity lithium peroxide necessitates the use of a redox mediator (RM) to facilitate the charging process; however, RMs can also be degraded by 1O2, which limits their efficacy in the long term. Recently, it was revealed that certain RMs play a role in suppressing the generation of 1O2. In this review, the relationship between the RM and 1O2 is described. Based on recent understandings, clear insight into RM reactions toward 1O2 and possible future research directions will be provided.