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

Authors
Kwak, Won-JinKim, HunPetit, Yann K.Leypold, ChristianTrung Thien NguyenMahne, NikaRedfern, PaulCurtiss, Larry A.Jung, Hun-GiBorisov, Sergey M.Freunberger, Stefan A.Sun, Yang-Kook
Issue Date
2019-03
Publisher
Nature Publishing Group
Citation
Nature Communications, v.10
Abstract
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.
Keywords
LI-O-2 BATTERIES; ENE REACTIONS; ELECTROLYTE; SUPEROXIDE; STABILITY; CHARGE; LI2O2; INTERMEDIATE; DEGRADATION; CHEMISTRY
ISSN
2041-1723
URI
https://pubs.kist.re.kr/handle/201004/120275
DOI
10.1038/s41467-019-09399-0
Appears in Collections:
KIST Article > 2019
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