First principles study of the adsorption of alkali metal ions (Li, Na, and K) on Janus WSSe monolayer for rechargeable metal-ion batteries

Two-dimensional (2D) materials with high specific capacities and superior physical properties are essential for designing rechargeable metal-ion batteries. In this study, first-principles calculations were performed to evaluate the potential of a WSSe monolayer as an electrode material for rechargeable lithium (Li), sodium (Na), and potassium (K) ion batteries. Our results showed that all alkali adsorptions were energetically stable and caused a semiconductor-to-metal transition, improving electronic conductivity. The calculated open-circuit voltage (OCV) for Li ions (0.48 V), Na ions (0.57 V), and K ions (0.37 V) was less than 1 V, which is critical for high charge and discharge rates. The maximum theoretical capacities for Li, Na, and K atoms adsorbed on the Janus WSSe monolayer were 477.8, 371.5, and 156.0 mAh/g, respectively. Our calculated migration energy barriers for Li, Na and K on S layer (Se layer) are (0.25, 0.07 and 0.07 (0.18, 0.04 and 0.038) eV, respectively, suggesting that the Se layer experiences faster Li-ion diffusion than the S layer. The ion diffusion potential for Li, Na, and K on the S layer (Se layer) for path 1 was considerably lower than paths 2 and 3, suggesting that the Se layer has faster Li-ion diffusion than the S layer. These findings provide a promising avenue for designing high-performing anode materials for rechargeable metal-ion batteries.