Effect of singlet oxygen on redox mediators in lithium-oxygen batteries

The use of a redox mediator (RM) to chemically decompose Li2O2 is an efficient approach to improve the efficiency and cyclability of lithium-oxygen batteries. It has been suggested that RMs can react with the singlet oxygen (O-1(2)) but no attempt has been made to categorize the reactivity of different RMs with O-1(2), or investigate the impact of this reaction on the electrochemical behavior of RMs. Here we show that the reactivity of RMs with O-1(2) depends on the unique chemistry of the RM, and that the Li2O2 decomposition kinetics of RMs are considerably affected by their reactivity towards O-1(2). We examine changes to the chemical and electrochemical properties of RMs after exposure to O-1(2). These results suggest that the activity and lifetime of RMs in Li-O-2 cells are affected by their reactivity towards O-1(2), and that RMs can be classified depending on how easily they react with, or physically quench O-1(2).