Two-dimensional (2D) titanium disulfide (TiS) is the lightest transition-metal dichalcogenide (TMD). It exhibits relatively better adsorption and diffusion of sodium (Na) and potassium (K) ions than other TMDs, such as MoS (molybdenum disulfide) and ReS (rhenium disulfide), making it a promising anode material for alkali-ion batteries. Previous studies have found that doping significantly enhances the adsorption and diffusion capabilities of 2D TMDs. For the first time, this work reports the adsorption of Na and K ions on doped TiS monolayers using first-principles calculations, where the Ti atom is substituted by 3d-transition metals, including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). Metal-atom doping induces remarkably stronger binding of alkali ions on the surface of TiS, with adsorption energies ranging from 2.07 to 2.48 eV for Na and 2.59 to 3.00 eV for K. The diffusion barrier energies for alkali ions decrease in the proximity of the doping site and increase as the ions travel away from the doping site for Fe-, Co-, and Ni-doped TiS. The average open circuit voltage increases dramatically when Na ions are adsorbed on Fe-doped TiS (by 62%) and Co-doped TiS (by 61%), while K ions result in a moderate improvement of 9% and 8%, respectively. These findings suggest that metal-atom doping considerably improves the electrochemical properties of 2D TiS, potentially enabling its use as anode materials in Na- and K-ion batteries.
Dopant-enhanced sodium and potassium-ion adsorption and diffusion in two-dimensional titanium disulfide
A. K. Nair, C. M. Da Silva, C. H. Amon; Dopant-enhanced sodium and potassium-ion adsorption and diffusion in two-dimensional titanium disulfide. J. Appl. Phys. 14 February 2023; 133 (6): 064302. https://doi.org/10.1063/5.0132894
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