1 research outputs found
Poly(vinylidene fluoride) (PVDF) Binder Degradation in Li–O<sub>2</sub> Batteries: A Consideration for the Characterization of Lithium Superoxide
We
show that a common Li–O<sub>2</sub> battery cathode binder,
polyÂ(vinylidene fluoride) (PVDF), degrades in the presence of reduced
oxygen species during Li–O<sub>2</sub> discharge when adventitious
impurities are present. This degradation process forms products that
exhibit Raman shifts (∼1133 and 1525 cm<sup>–1</sup>) nearly identical to those reported to belong to lithium superoxide
(LiO<sub>2</sub>), complicating the identification of LiO<sub>2</sub> in Li–O<sub>2</sub> batteries. We show that these peaks are
not observed when characterizing extracted discharged cathodes that
employ polyÂ(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 LiO<sub>2</sub> formation.
We confirm that for all extracted discharged cathodes on which the
1133 and 1525 cm<sup>–1</sup> Raman shifts are observed, only
a 2.0 e<sup>–</sup>/O<sub>2</sub> process is identified during
the discharge, and lithium peroxide (Li<sub>2</sub>O<sub>2</sub>)
is predominantly formed (along with typical parasitic side product
formation). Our results strongly suggest that bulk, stable LiO<sub>2</sub> formation via the 1 e<sup>–</sup>/O<sub>2</sub> process
is not an active discharge reaction in Li–O<sub>2</sub> batteries