title: Poly(vinylidene fluoride) (PVDF) Binder Degradation in Li-O2Batteries: A Consideration for the Characterization of Lithium Superoxide.
abstract: We show that a common Li-O2battery cathode binder, poly(vinylidene fluoride) (PVDF), degrades in the presence of reduced oxygen species during Li-O2discharge when adventitious impurities are present. This degradation process forms products that exhibit Raman shifts (∼1133 and 1525 cm-1) nearly identical to those reported to belong to lithium superoxide (LiO2), complicating the identification of LiO2in Li-O2batteries. We show that these peaks are not observed when characterizing extracted discharged cathodes that employ poly(tetrafluoroethylene) (PTFE) as a binder, even when used to bind iridium-decorated reduced graphene oxide (Ir-rGO)-based cathodes similar to those that reportedly stabilize bulk LiO2formation. We confirm that for all extracted discharged cathodes on which the 1133 and 1525 cm-1Raman shifts are observed, only a 2.0 e-/O2process is identified during the discharge, and lithium peroxide (Li2O2) is predominantly formed (along with typical parasitic side product formation). Our results strongly suggest that bulk, stable LiO2formation via the 1 e-/O2process is not an active discharge reaction in Li-O2batteries.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Joseph K
authors.identifier: http://orcid.org/0000-0002-7982-6096
authors.initials: JK
authors.lastname: Papp
authors.affiliation: The Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Forster
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Colin M
authors.identifier: http://orcid.org/0000-0002-8826-0944
authors.initials: CM
authors.lastname: Burke
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Hyo Won
authors.initials: HW
authors.lastname: Kim
authors.affiliation: SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.|SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Luntz
authors.affiliation: IBM Almaden Research Center , San Jose, California 95120, United States.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Shelby
authors.affiliation: The Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Urban
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Bryan D
authors.identifier: http://orcid.org/0000-0001-6599-2336
authors.initials: BD
authors.lastname: McCloskey