Atomic Sulfur Anchored on Silicene, Phosphorene and Borophene for Excellent Cycle Performance of Li-S Batteries

For the first time, atomic sulfur is incorporated into silicene, phosphorene and borophene to intrinsically eliminate the dissolution of LiPS. A high atomic sulfur coverage (63.1 wt%) is achieved in silicene and concomitantly stabilizes the silicene layer. For the S₃-covered silicene, a high theoretical capacity of 857 mA h g^-1 is achieved with slight dissolution of LiPS originated from the loss of interior S atoms that are not directly bound with silicene surface. By realizing the elemental S₂ coverage on silicene with large surface area, the Li⁺ ions can react fast with the S₂ species, leading to a high theoretical capacity of 891 mA h g^-1 without dissolution and migration of the intermediate LiPS. Most interestingly, the discharge products of atomic layer of lithium sulfides on silicene surface exhibit completely different behaviors with the traditional discharge products of solid Li₂S, which can function as effective adsorption and activation sites for the conversion of LiPS from long-chain to short-chain by accelerated redox reaction. The present study gains some key insights into how the atomic sulfur contributes to the intrinsic shuttle inhibition and offers a feasible way to design the atomic sulfur based cathode of Li-S batteries with better electrochemical performance.