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 Li2S 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 Li2S is scarce. Using density functional theory calculations, we proposed a procedure to screen catalytic hosts for solid and non-solid reactions of Li2S2/Li2S by employing the available functionalized Ti3C2T2 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 Ti3C2Se2 is the optimal candidate for improving the reaction kinetics of solid Li2S. Suitable catalysts for different reaction processes between molecular Li2S2 and Li2S 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 Li2S. 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.