Investigation of the Cathode-Catalyst-Electrolyte Interface in Aprotic Li-O₂ Batteries

Enabled by a unique integrated fabrication and characterization platform, X-ray photoelectron spectroscopy (XPS) studies reveal the formation of a thin solid electrolyte interphase (SEI) layer on a Li-O₂ cathode after the first cycle. Subsequent cycling indicates that this SEI layer is very stable in terms of both chemistry and morphology, even after extensive cycling, preserving reversibility at the cathode/electrolyte interface. Remarkably, even after cell failure, replacement of the lithium anode resulted in recovery of the cycling behavior with the same cathode. These results demonstrate that chemical stabilization of the cathode/electrolyte interface promotes long-term operation of DMSO-based Li-O₂ Ru-catalyzed batteries. Characterization of the Li anode surface reveals electrolyte decomposition, and a partial mechanism is proposed for the observed chemical composition of the cathode SEI. These studies are enabled by conformal deposition of a heterogeneous OER catalyst on a freestanding, binder-free, mesoporous, carbon-based Li-O₂ cathode with high capacity and long-term cycling stability.