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

Abstract

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 (¹O₂) but no attempt has been made to categorize the reactivity of different RMs with ¹O₂, or investigate the impact of this reaction on the electrochemical behavior of RMs. Here we show that the reactivity of RMs with ¹O₂ depends on the unique chemistry of the RM, and that the Li₂O₂ decomposition kinetics of RMs are considerably affected by their reactivity towards ¹O₂. We examine changes to the chemical and electrochemical properties of RMs after exposure to ¹O₂. These results suggest that the activity and lifetime of RMs in Li–O₂ cells are affected by their reactivity towards ¹O₂, and that RMs can be classified depending on how easily they react with, or physically quench ¹O₂.