How does the active site in the MoSe2 surface affect its electrochemical performance as anode material for metal-ion batteries?

Abstract In this work, we implement density functional theory (DFT) simulations to study how active sites in the MoSe2 surface affect its electrochemical performance as anode material for metal-ion batteries (metal ions including Li, Na, K, Mg, and Al ions). Se vacancy MoSe2 (001) and MoSe2 (110) are considered to provide active sites for metal ions. The adsorption energies, diffusion energy barriers, electronic conductivity and open circuit voltage profile (OCV) are evaluated. According to our calculations, MoSe2 (001) with Se vacancy occupied by Mg ion shows similar diffusion energy barriers and comparable OCV to the pristine MoSe2 (001). Moreover, Mg ion shows much lower diffusion barriers than the other ions. Besides that, MoSe2 (110) shows much higher adsorption energies than the (001) section, indicating its high capacity for metal-ion batteries. However, MoSe2 (110) also exhibits much higher diffusion energy barriers, which would inhibit its rate capability. Comparatively, MoSe2 (001) with Se vacancies can improve the conductivity of MoSe2, and the conductivity increases with the number of Se vacancies increases. Consequently, MoSe2 (001) with single Se vacancy has comprehensive electrochemical performance for Mg-ion battery anode, including low Mg-ion diffusion energy, comparable OCV, and high electronic conductance.