Understanding the anchoring behavior of titanium carbide-based MXenes depending on the functional group in Li-S batteries: A density functional theory study

Abstract

In this study, the properties of F-functionalized Ti₂C (Ti₂CF₂) and O-functionalized Ti₂C (Ti₂CO₂) as conductive anchoring materials for lithium-sulfur (Li-S) batteries were investigated using the density functional theory (DFT). It was confirmed that both of Ti₂CF₂ and Ti₂CO₂ will suppress the shuttle effect by different suppressing mechanisms depending on the Ti₂CF₂ and Ti₂CO₂. The F-functionalized surface of Ti₂CF₂ suppresses the shuttle effect by strong interaction with lithium polysulfides (LiPSs). On the other hand, the shuttle effect is suppressed on the O-functionalized surface by converting soluble high order LiPSs (Li₂S8, Li₂S7, and Li₂S₆) to insoluble elemental sulfur. In addition, the redox reaction of anchored LiPSs takes place because Ti₂CF₂ and Ti₂CO₂ show metallic properties after anchoring the LiPSs. As a result, the F and O-functionalized surfaces of the Ti₂C-based MXenes will contribute to suppressing the shuttle effect as conductive anchoring materials for Li-S batteries. This theoretical study will provide further insight into the application of MXenes as a conductive anchoring material for Li-S batteries.