A Spin-polarized DFT study of functionalized MXenes as effective anchor materials in lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries have attracted great enthusiasm in recent years due to ultra-high theoretical energy densities, abundant sulfur electrode resources and low price. Despite the severe shuttle effect of lithium polysulfides (LiPSs), the poor conductivity of S and its intermediate products, and the relatively slow dynamics, pose significant challenges for the commercial application of Li-S batteries. Here, functionalized MXenes MCT (M = V, Cr, Mn, and Mo; T = F and O) used as the sulfur host are studied to build multifunctional cathodes spin-polarized first-principles calculation. Through analyzing the adsorption energy and configuration of S/LiS adsorbed MCT, it is found that spin polarization is indispensable to the Li-S battery calculation of MXenes with transition metals. With the spin polarization calculation, the MCT exhibit moderate anchoring strengths and stable adsorption structures, which effectively mitigates the polysulfide shuttle phenomenon. The low decomposition barriers of LiS (0.27-1.00 eV) and low diffusion barriers of Li (0.11-0.44 eV) of MCT are observed, which effectively improve the rate performance of batteries. Among the studied MXenes, VCO and MoCO are the best choices of host materials for LiPSs with metallic characteristics, outstanding electrocatalysis performance, low decomposition barriers of LiS, and diffusion barriers of Li. This work provides important insights into spin-polarized electrode materials for enhanced energy storage capabilities by investigating the application of intrinsic magnetic MXene compounds.