Absorption and diffusion of lithium on layered InSe

Abstract Two-dimensional indium selenide (InSe) is attracting much recent attention due to its high electron mobility. Using ab initio calculations, we systematically investigate the absorption and diffusion of lithium (Li) ion inside layered InSe. We find that firstly the binding energy absolute values for Li-ion absorbed on bulk and monolayer (ML) InSe range from 0.43 to 1.61 eV, which are large enough to stabilize Li–InSe systems. The absolute value of the binding energy is also approximately monotonically decreased with the increasing of Li-ion density. Secondly, the structure of InSe isn't deformed much by the insertion of Li, and the largest crystalline size change is only 4.68%, indicating the robustness of InSe against the insertion of Li ions. Thirdly, the diffusion barriers heights for Li ions diffusion inside bulk and ML InSe are 0.02–0.06 eV and 0.18–0.24 eV, respectively, and the diffusion barrier heights monotonically decrease with the increasing of Li-ion density. Finally, after the absorption of Li ions, InSe transforms from semiconductor to metal, rendering Li–InSe systems as good electrical conductors.