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.