Authors: Shiming Li, Daoling Peng.
Lithium-sulfur (Li-S) batteries are widely considered to be one of the most promising next-generation energy- storage systems due to its high theoretical energy density. But there are still some problems, including of the shuttling of lithium polysulfides (LiPSs; Li2 Sn , n=2, 4, 6 or 8) and sluggish decomposition of solid Li2 S, seriously hinder its practical application. Since Co4 N has showed its capability to alleviate shuttle effect and accelerate electrode reactions kinetics on S cathode, which can effectively improve Li-S batteries performance. We theoretically investigated the adsorption properties and conversion mechanisms of the LiPSs species on the Co4 N(111) surface by the first-principle density functional theory (DFT) calculations. Both the electronic structures of LiPSs and the chemical and physical properties of Co4 N were studied. The free energy pathway of Li2 S decomposition on the considered surface was modeled by a suggested stepwise cathodic delithium reaction mechanism. A series of transition state structures were obtained and low barrier energies were found, indicating that Co4 N could be a good candidate for the research of lithium-sulfur batteries.
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