Adsorption And Diffusion Of Lithium On The MoS₂Monolayer

Based on Density Functional Theory, the lithium adsorption and diffusion on theMoS2monolayer are studied in this thesis.1. We first study the adsorption behavior of a single lithium atom and the bindingenergy under different external strain on the1H-MoS2monolayer，in order to study itspotential application as anode materials for lithium ion batteries. Results show that thelithium adsorption energy reaches a lowest value when the adsorption height is1.46at the top of a Mo atom，and the binding energy decreases with tensile strain orcompressive strain. Next, we focus on the adsorption behavior of more lithium atomson the1H-MoS2monolayer，we note that the binding energy is also not sensitive tolithium concentration. The lithium atom dissociation path on the1H-MoS2monolayeris optimized by the NEB method. The calculated diffusion barrier for a single lithiumadatom and seventeen lithium adatoms on the1H-MoS2monolayer respectively is0.21eV and0.25eV，indicating that the lithium concentration has a weak effect onthe diffusion of lithium adatom. Then, the diffusion barriers of a single lithiumadatom on the1H-MoS2monolayer under external strain are examined，we find thelithium ion diffusion energy barriers are increased with tensile strains while decreasedwith compressive strains，but the diffusion energy barrier changes only0.03eV.2. We also first study the adsorption behavior of a single lithium atom and thebinding energy of more lithium atoms on one side and two sides of the1T-MoS2monolayer. Results show that the lithium adsorption energy reaches a lowest value isnot at the right top site of a Mo atom, but deviating a little along one Mo-S bond.Thebinding energy of single lithium atom decreases with the increase of the lithium atomseither for adsorption on one side or on two sides，but it is still larger than the bindingenergy of lithium metal，which means the dendritic crystal could not be formed whenthe1T-MoS2is used to be the electrode material. for low lithium concentration orhigh，the1T-MoS2are also metallic. The lithium atom dissociation path on the1T-MoS2monolayer is optimized by the NEB method. The calculated diffusionbarrier for a single lithium adatom and seventeen lithium adatoms on the1T-MoS2monolayer respectively is0.52eV and0.35eV，which shows the diffusion barrier oflithium on1T-MoS2is larger than that on1H-MoS2，Even so, the diffusion barriers oflithium on1T-MoS2could still be acceptable as the electrode material for the LIBs.