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

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. (C) 2016 Elsevier B.V. All rights reserved.