Kwak, Won-Jin Kim, Hun Petit, Yann K. Leypold, Christian Trung Thien Nguyen Mahne, Nika Redfern, Paul Curtiss, Larry A. Jung, Hun-Gi Borisov, Sergey M. Freunberger, Stefan A. Sun, Yang-Kook 2024-01-19T20:33:08Z 2024-01-19T20:33:08Z 2021-09-02 2019-03 2041-1723 https://pubs.kist.re.kr/handle/201004/120275 Non-aqueous lithium-oxygen batteries cycle by forming lithium peroxide during discharge and oxidizing it during recharge. The significant problem of oxidizing the solid insulating lithium peroxide can greatly be facilitated by incorporating redox mediators that shuttle electron-holes between the porous substrate and lithium peroxide. Redox mediator stability is thus key for energy efficiency, reversibility, and cycle life. However, the gradual deactivation of redox mediators during repeated cycling has not conclusively been explained. Here, we show that organic redox mediators are predominantly decomposed by singlet oxygen that forms during cycling. Their reaction with superoxide, previously assumed to mainly trigger their degradation, peroxide, and dioxygen, is orders of magnitude slower in comparison. The reduced form of the mediator is markedly more reactive towards singlet oxygen than the oxidized form, from which we derive reaction mechanisms supported by density functional theory calculations. Redox mediators must thus be designed for stability against singlet oxygen. English Nature Publishing Group Deactivation of redox mediators in lithium-oxygen batteries by singlet oxygen Article 10.1038/s41467-019-09399-0 1 Nature Communications, v.10 Nature Communications 10 Y scie scopus 000462288800011 2-s2.0-85063451222 Multidisciplinary Sciences Science & Technology - Other Topics Article LI-O-2 BATTERIES ENE REACTIONS ELECTROLYTE SUPEROXIDE STABILITY CHARGE LI2O2 INTERMEDIATE DEGRADATION CHEMISTRY