Computational screening of functionalized MXenes to catalyze the solid and non-solid conversion reactions in cathodes of lithium-sulfur batteries.

The poor cycling abilities of S cathodes due to the dissolution of high-order lithium polysulfides and sluggish reaction kinetics of low-order solid Li 2 S hinder the commercial application of lithium-sulfur batteries. Although many hosts have been introduced into S electrodes to anchor high-order polysulfides, an effective procedure to select the hosts to improve the conversion kinetics of solid Li 2 S is scarce. Using density functional theory calculations, we proposed a procedure to screen catalytic hosts for solid and non-solid reactions of Li 2 S 2 /Li 2 S by employing the available functionalized Ti 3 C 2 T 2 MXenes (T = H, O, F, S, Cl, Se, Te, Br, OH, and NH), under the precondition of good anchoring abilities for high-order polysulfides. For the solid-state reactions, it was found that Ti 3 C 2 Se 2 is the optimal candidate for improving the reaction kinetics of solid Li 2 S. Suitable catalysts for different reaction processes between molecular Li 2 S 2 and Li 2 S have also been proposed. We also proposed that sulfur cathodes doped with heavy atoms (Se or Te) belonging to the main group VI may significantly modify the reaction kinetics of Li 2 S. These results provide guidance on synthesizing MXenes with the given surface groups as the hosts and can accelerate the step of finding out other suitable host materials.