Mechanism on the Improved Performance of Lithium Sulfur Batteries with MXene-Based Additives

The loss of sulfur in the cathode of a lithium sulfur battery (LSB) severely hinders the practical application of LSBs, and so do the insulativity of S and its lithiation end products. The incorporation of MXene can significantly improve the performance of LSBs; however, the underlying mechanism at the atomic scale has not been deeply explored. In the present work, by using density functional theory calculations, we systemically studied the interactions of lithium (poly)sulfides (Li2Sm) on Ti-based bare MXenes (TinXn–1) and surface functionalized Ti2C with −F, −O, and −OH groups. Through analyzing the geometric and electronic structures, binding energies, and deformation charge densities of Li2Sm adsorbed MXenes, we found that the strong Ti–S bonds dominate the interactions between Li2Sm and MXenes. The strong Coulombic interactions help cathodes to confine S from dissolution. Besides, the conductivities of MXenes and Li2Sm@MXenes are beneficial for the overall performance of the LSB. These will provide in-depth theoretical guidance support for the utilization of MXene in LSBs.