Adsorption and migration of Li-ion in layered SnSe 2 : a first principle study

The properties of Li-ion adsorption and migration in layered SnSe2 are systematically investigated using the first principle calculations. It is found that the Li atoms are adsorbed strongly on substrate SnSe2, and the binding energy (>3eV) is significantly higher than those on graphene, phosphorene, MoS2, and some other two-dimensional (2D) layered materials. Bader charge analysis reveals that almost the whole charge of 2s electron of the Li atom transfers to substrate SnSe2 and Li exists in the cationic state. The Li-ion migration energy barrier for monolayer SnSe2 is 0.197eV, which is significantly lower than those for graphene, MoS2, and other 2D materials. The average open-circuit voltage of 3.05V is predicted in the monolayer SnSe2-based Li-ion battery. The Li intercalation also leads to a transition from semiconductor to metallic state and gives rise to a good electrical conductivity. These findings provide insights into the Li-ion adsorption properties and migration mechanism in layered transition-metal dichalcogenide.