title: Singlet Oxygen Formation during the Charging Process of an Aprotic Lithium-Oxygen Battery.
abstract: Aprotic lithium-oxygen (Li-O2 ) batteries have attracted considerable attention in recent years owing to their outstanding theoretical energy density. A major challenge is their poor reversibility caused by degradation reactions, which mainly occur during battery charge and are still poorly understood. Herein, we show that singlet oxygen ((1) Δg ) is formed upon Li2 O2 oxidation at potentials above 3.5 V. Singlet oxygen was detected through a reaction with a spin trap to form a stable radical that was observed by time- and voltage-resolved in operando EPR spectroscopy in a purpose-built spectroelectrochemical cell. According to our estimate, a lower limit of approximately 0.5 % of the evolved oxygen is singlet oxygen. The occurrence of highly reactive singlet oxygen might be the long-overlooked missing link in the understanding of the electrolyte degradation and carbon corrosion reactions that occur during the charging of Li-O2 cells.
authors.affiliation: Technische Universität München, Chair for Technical Electrochemistry, Department of Chemistry and Catalysis Research Center, Germany. johannes.wandt@tum.de.
authors.forename: Johannes
authors.identifier: 0000-0002-9175-2616
authors.initials: J
authors.lastname: Wandt
authors.affiliation: Forschungszentrum Jülich, Institut für Energie- und Klimaforschung, Grundlagen der Elektrochemie (IEK-9), 52425, Jülich, Germany. p.jakes@fz-juelich.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Jakes
authors.affiliation: Forschungszentrum Jülich, Institut für Energie- und Klimaforschung, Grundlagen der Elektrochemie (IEK-9), 52425, Jülich, Germany.|RWTH Aachen University, Institut für Technische und Makromolekulare Chemie, 52074, Aachen, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Granwehr
authors.affiliation: Technische Universität München, Chair for Technical Electrochemistry, Department of Chemistry and Catalysis Research Center, Germany.
authors.forename: Hubert A
authors.initials: HA
authors.lastname: Gasteiger
authors.affiliation: Forschungszentrum Jülich, Institut für Energie- und Klimaforschung, Grundlagen der Elektrochemie (IEK-9), 52425, Jülich, Germany.|RWTH Aachen University, Institut für Physikalische Chemie, 52074, Aachen, Germany.
authors.forename: Rüdiger-A
authors.initials: RA
authors.lastname: Eichel
keywords: EPR spectroscopy; carbon corrosion; charging mechanism; lithium-air batteries; singlet oxygen