Deactivation of redox mediators in lithium-oxygen batteries by singlet oxygen

Won-Jin Kwak, Hun Kim, Yann Kevin Petit, Christian Leypold, Trung Thien Nguyen, Nika Mahne, Paul Redfern, Larry A. Curtiss, Hun-Gi Jung, Sergey Borisov, Stefan Freunberger, Yang-Kook Sun

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Article number1380
Number of pages8
JournalNature Communications
Issue number1
Publication statusPublished - 26 Mar 2019

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)

Fields of Expertise

  • Advanced Materials Science

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