Monolayer MSi₂P₄ (M = V, Nb, and Ta) as Highly Efficient Sulfur Host Materials for Lithium-Sulfur Batteries

Despite the high capacity and low cost of lithium-sulfur (Li-S) batteries, their commercialization is greatly blocked by multiple bottlenecks including the shuttle effect of lithium polysulfides (LiPSs), poor conductivity of sulfur, and sluggish reaction kinetics. Herein, we propose novel two-dimensional MSi₂P₄ (M = V, Nb, and Ta) monolayers as promising sulfur hosts to improve the Li-S battery performance. Our calculations show that MSi₂P₄ monolayers offer moderate binding strengths to the polysulfides, which are expected to effectively inhibit the LiPS shuttling and dissolution. Moreover, the conductive properties of the MSi₂P₄ systems are well maintained after LiPS adsorption, eliminating the insulating nature of sulfur species. Remarkably, MSi₂P₄ monolayers exhibit superior electrocatalytic activity for the sulfur reduction reaction and the Li₂S decomposition reaction, which considerably lowers the energy barriers of LiPS conversions during discharge and charge, thus ensuring the fast redox kinetics and high sulfur utilization of Li-S batteries. This study pioneers the application of MSi₂P₄ monolayers as highly efficient sulfur host materials for Li-S batteries and affords insights for further development of advanced Li-S batteries.