Infrared spectroscopy studies on stability of dimethyl sulfoxide for application in a LI-air battery

Abstract

In situ infrared subtractive normalized Fourier transform infrared spectroscopy (SNIFTIRS) experiments performed simultaneously with the electroreduction of oxygen on gold and platinum cathodes in LiPF6 dimethyl sulfoxide (DMSO) electrolyte have shown that the solvent is stable with respect to nucleophilic attack by the electrogenerated superoxide radical anion. However, long-term experiments with KO2 solutions in DMSO have shown a slow formation of dimethyl sulfone. Evidence of dimethyl sulfone formation by anodic oxidation of DMSO above 4.2 V (Li/Li+) in the presence of trace water has been obtained on gold. On platinum, this unwanted reaction in the charging cycle of a lithium−air battery takes place at lower potentials, i.e., 3.5 V.