Halogen-Doping Effect on the Delithiation and Charge Transfer of (Li2S)10 Cluster.

Previous studies have suggested beneficial effects in lithium-sulfur batteries containing iodide in a sulfur-based cathode or as an electrolyte additive. These effects include preventing electrolyte degradation and improving the cycle stability of Li-S cells. However, little is known regarding the underlying reasons of such performance improvements. In this work, we present a theoretical study of the halogen-doping effect on the delithiation (charge) process on a (Li2S)10 model structure representing a potential final discharge product. It is revealed that the electron polaron is the dominant charge carrier during the charge process, and iodine is a facilitating agent for lithium detachment from the lithium sulfide cluster. However, the graphene support was found as potentially slowing down the ionic transport during the delithiation process due to charge transfer exerted by the support to the doped cluster that may retain the positive ions in the particle.