Functionalized titanium nitride-based MXenes as promising host materials for lithium-sulfur batteries: A first principles study

Searching conductive host materials to suppress the shuttle effect is a long-term goal in the development of lithium-sulfur (Li-S) batteries. In this work, first principles calculations were carried out to systematically investigate O-functionalized Ti2N (Ti2NO2) and F-functionalized Ti2N (Ti2NF2) monolayers as host materials to anchor the soluble Li(2)Sx species. Our results demonstrate that both Ti2NO2 and Ti2NF2 not only possess moderate adsorption energies towards Li(2)Sx species, but also achieve a good balance between adsorption energies and intactness of Li2Sx species, which could avoid the dissolution of Li2Sx species into electrolyte solvents and improve the utilization of active materials. In addition, after adsorption of S-8 and Li2Sx species, the metallic character of Ti2NO2 and Ti2NF2 is still preserved, which benefits the redox reaction of Li2Sx species. Given these exceptional properties, it is expected that Ti2NO2 and Ti2NF2 could be promising host materials for Li-S batteries with good cycling performance.