Cycling non-aqueous lithium-air batteries with dimethyl sulfoxide and sulfolane co-solvent

Despite considerable research efforts, finding a chemically stable electrolyte mixture in the presence of reduced oxygen species remains a great challenge. Previously, dimethyl sulfoxide (DMSO) and sulfolane-based electrolytes were reported to be stable for Li-O2 battery applications. Recently LiOH-based chemistries have demonstrated to involve supressed side reactions in water-added ether- and DMSO-based electrolytes. Herein, we investigate the impact of dimethyl sulfoxide-based electrolyte and sulfolane co-solvent on the cell chemistry in the presence of water. We found that DMSO-based electrolyte leads to formation of a peroxide-hydroxide mixture as discharge products and the removal of both LiOH and Li2O2 on charging from 3.2 -3.6 V (vs. Li+/Li) is observed. In the presence of sulfolane as co-solvent, a mixture of Li2O2 and LiOH is formed as major discharge products with slightly more dominant LiOH formation than in the absence of sulfolane. The presence of sulfolane has also significant effects in the charging behaviour, exhibiting a clearer 3 e-/O2 oxygen evolution reaction profile during the entire charging process. This work provides insights into understanding the effects of the primary solvent on promoting LiOH formation and decomposition in LiI mediated non-aqueous Li-O2 batteries.