A model cathode for mechanistic study of organosulfide electrochemistry in Li-organosulfide batteries

Organosulfides offer new opportunities for high performance lithium-sulfur(Li-S) batteries because of materials abundance, versatile structures and unique properties. Yet, their redox kinetics as well as cycling performance need to be further improved. Employing redox mediators is a highly effective strategy to address above challenges. However, the underlying mechanism in this chemistry is so far insufficiently explored. Here, phenyl disulfide(Ph S–SPh) and phenyl diselenide(Ph Se–Se Ph) are used as a model system for mechanistic understanding of organosulfide electrochemistry, particularly the rate acceleration. Profiling the reaction thermodynamics and charge-discharge process reveals redox of both S–S and C–S bonds, as well as that the coupling between radical exchange and electrochemical redox is the key to enhance the sulfur kinetics. This study not only establishes a basic understanding of orgaonsulfide electrochemistry in Li-S batteries, but also points out a general strategy for enhancing the kinetics of sulfur electrodes in electrochemical devices.