Unraveling the Reaction Interfaces and Intermediates of Ru-Catalyzed LiOH Decomposition in DMSO-Based Li-O2 Batteries.

Investigation of LiOH decomposition in nonaqueous electrolytes not only expands the fundamental understanding of four-electron oxygen evolution reactions in aprotic media but also is crucial to the development of high-performance lithium-air batteries involving the formation/decomposition of LiOH. In this work, we have shown that the decomposition of LiOH by ruthenium metal catalysts in a wet DMSO electrolyte occurs at the catalyst-electrolyte interface, initiated via a potential-triggered dissolution/reprecipitation process. The in situ UV-vis methodology devised herein provides direct experimental evidence that the hydroxyl radical is a common reaction intermediate formed in several nonaqueous electrolytes; this method is applicable to study other battery systems. Our results highlight that the reactivity of the hydroxyl radical toward nonaqueous electrolyte represents a major factor limiting O2 evolution during LiOH decomposition. Coupling catalysts restraining hydroxyl reactivity with electrolytes more resistant to hydroxyl radical attack could help improve the reversibility of this reaction.