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

Abstract

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 (Li 2 S) 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.

Molecular engineering of sulfur‐providing materials for optimized sulfur conversion in Li‐S chemistry

“…Based on theoretical calculations, Fomine and coworkers further analyzed the impacts of doping with halogen atoms on the structure, electronic and charge transfer properties of Li 2 S during the delithiation (charging) process 61 . It is revealed that, due to the more negative formation energy than that of pristine Li 2 S, the lithium is easier to extract from the iodine doped Li 2 S cluster during the first delithiation process.…”

Silver Iodide as a Host Material of Sulfur for Li–S Battery

“…Previous work has suggested proper amount of LiI is beneficial to the electrochemical performance because LiI with ionic conductivity of 10 −7 s cm −1 can improve the ionic conductivity of the electrode and induce the formation of a protective coating. [42][43][44][45] Such protective coating can inhibit the release of polysulfides into the electrolyte on the cathode side and prevent the reduction of polysulfides on the anode side, minimizing the shuttle effect and improving the Coulombic efficiency as well as the utilization of active materials. Furthermore, metallic Ag is thought to increase the electronic conductivity in the electrode and reduce the electrochemical resistance.…”