Anchoring effects of S-terminated Ti2C MXene for lithium-sulfur batteries: A first-principles study

The low cycle stability and low efficiency of lithium-sulfur (Li-S) batteries stemming from the dissolution and diffusion of lithium polysulfides in the electrolyte severely hinder their commercialization. Using first-principles calculations, we demonstrate that the strong Ti-S interaction leads to stable S-terminated Ti2C MXene (Ti2CS2). Compared with other surface-functionalized Ti2C MXenes, such as Ti2CO2 and Ti2CF2, Ti2CS2 has the highest binding energy to polysulfides and thus highest efficiency to suppress the shuttle phenomenon of polysulfides. In addition, the metallic features of Ti2CS2 facilitate the electrochemical activity during the charge (or discharge) process. The diffusion of Li ions on Ti2CS2 experiences a relatively low energy barrier which is expected to assist the electrochemical process. These results provide a surface-functionalization strategy to design of sulfur host materials for high performance Li-S batteries.