Uniaxial tensile strain impact on 1T-NbS2 monolayers as cathode material for lithium–sulfur batteries†

Abstract

The application of lithium–sulfur (Li–S) batteries as efficient energy storage systems is hindered by the polysulfide shuttle and expansion effects. To overcome these obstacles, we employed density functional theory (DFT) to explore the 1T-NbS₂ monolayer as a cathode material for Li–S batteries, particularly focusing on the effects of uniaxial tensile strain. Our results indicate that the pristine 1T-NbS₂ monolayer presents a balanced adsorption affinity for LiPSs, thereby mitigating the shuttle effect. The bond formation information is investigated through comprehensive analysis of charge transfer, physical/chemical adsorption, and projected crystal orbital Hamiltonian population (pCOHP). The projected density of states (PDOS) analysis reveals the role of sulfur atoms near the Fermi surface in the lithiation process. Notably, the system keeps superior metallic characteristics, alongside a diminished decomposition energy barrier (0.45 eV), lowered lithium-ion migration energy barrier (0.16 eV), and a diminished positive Gibbs free energy change (0.41 eV) during the sulfur reduction reaction (SSR). The imposition of uniaxial tensile strain on the 1T-NbS₂ monolayer improves its adsorptive capacity for LiPSs and bolsters the retention of lithium–sulfur aggregates. These insights underscore the role of tensile strain in amplifying the efficiency of two-dimensional transition metal dichalcogenides as cathode materials of Li–S batteries.