Possible Causes of Lithium–Sulfur Battery Degradation

To assess the possible degradation mechanisms of lithium–sulfur batteries during their cycling, cyclic voltammograms of sulfur electrode in normalized coordinates were analyzed. A capacity decrease at the low-voltage plateau is shown to correspond to the decrease in the active material amount, whereas decrease at the high-voltage plateau is characterized by a decrease in the reduction depth. The sulfur solubility in the dioxolane–dimethoxyethane mixture (1 : 1) is measured; it is about 0.2 M at room temperature. It is concluded that the shuttle transfer of polysulfides is not the only cause of the degradation: the transfer of dissolved sulfur also makes a significant contribution.