One of the primary challenges impeding realization of the non-aqueous Li-O2 battery is finding a solvent that is chemically and electrochemically stable under cell operating conditions. Dimethyl sulfoxide (DMSO) is an attractive candidate for rechargeable Li-O₂ battery studies; however, there is still significant controversy regarding its stability on the Li-O₂ cathode surface.  

We report here results from a model  cathode system featuring various atomic layer deposited (ALD) catalysts including Ru, RuO₂, and Pt on a mesoporous CNT sponge to study the OER/ORR behavior in DMSO-based Li-O₂ cells. We performed multiple experiments (in-situ XPS, FTIR, Raman, and XRD) which assess the stability of the DMSO-Li₂O₂ interface and report perspectives on previously published studies. Our electrochemical experiments demonstrate long term, stable cycling of DMSO-based Li-O₂ cells.

This work is complemented by density functional theory calculations of DMSO degradation pathways on Li₂O₂.

Both experimental and theoretical evidence strongly suggest that oxidation of DMSO on the surface of Li₂O₂ is very unlikely to spontaneously occur and will take place only under certain conditions and to a minor extent under controlled operating voltages and in cell environments free of acidic function groups (either in the electrolyte or porous scaffold).