Understanding LiOH Chemistry in a Ruthenium-Catalyzed Li-O2 Battery

Tao Liu; Zigeng Liu; Gunwoo Kim; James T Frith; Nuria Garcia-Araez; Clare P Grey

doi:10.1002/anie.201709886

Understanding LiOH Chemistry in a Ruthenium-Catalyzed Li-O₂ Battery

Angew Chem Int Ed Engl. 2017 Dec 11;56(50):16057-16062. doi: 10.1002/anie.201709886. Epub 2017 Nov 21.

Authors

Tao Liu¹, Zigeng Liu¹, Gunwoo Kim¹, James T Frith², Nuria Garcia-Araez², Clare P Grey¹

Affiliations

¹ Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
² Department of Chemistry, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK.

Abstract

Non-aqueous Li-O₂ batteries are promising for next-generation energy storage. New battery chemistries based on LiOH, rather than Li₂ O₂ , have been recently reported in systems with added water, one using a soluble additive LiI and the other using solid Ru catalysts. Here, the focus is on the mechanism of Ru-catalyzed LiOH chemistry. Using nuclear magnetic resonance, operando electrochemical pressure measurements, and mass spectrometry, it is shown that on discharging LiOH forms via a 4 e^- oxygen reduction reaction, the H in LiOH coming solely from added H₂ O and the O from both O₂ and H₂ O. On charging, quantitative LiOH oxidation occurs at 3.1 V, with O being trapped in a form of dimethyl sulfone in the electrolyte. Compared to Li₂ O₂ , LiOH formation over Ru incurs few side reactions, a critical advantage for developing a long-lived battery. An optimized metal-catalyst-electrolyte couple needs to be sought that aids LiOH oxidation and is stable towards attack by hydroxyl radicals.

Keywords: Li-O2 batteries; LiOH; dimethyl sulfone; oxygen reduction/evolution; ruthenium catalysis.

Publication types

Research Support, Non-U.S. Gov't