Singlet Oxygen in Lithium−Oxygen Batteries

Abstract

AbstractSinglet oxygen (1O2) is one of the most critical species leading to parasitic side reactions and poor reversibility in non‐aqueous Li−O2 batteries. 1O2 is generated via the disproportionation of the superoxide radical (O2.−) in O2/Li2O2 electrochemistry. The mechanistic and computational studies on 1O2 formation revealed the significant roles of the associated cations, solvation ability of aprotic solvents, H+ source, and catalyst/electrode materials. Along with efforts to alleviate 1O2 production, trapping and eliminating 1O2 have been attempted using molecular agents. Anthracene derivatives trap 1O2 and form endoperoxides, which can be quantitatively detected using in situ fluorescence analysis. Physical quenchers that convert 1O2 to 3O2 are desirable for cycling of Li−O2 cells because quencher molecules are reusable. We highlight the recent reports on the formation and elimination of 1O2, and challenges and perspectives of suppressing the 1O2 effect on the performance of Li−O2 cells.