Mechanical Properties of Two-Dimensional Materials (Graphene, Silicene and MoS2 Monolayer) Upon Lithiation

Abstract

The mechanical stability of electrode materials in lithium-ion batteries (LIBs) is critical for their safe usage. Two-dimensional (2D) materials have been widely studied to be used as electrode materials for LIBs. In this paper, the mechanical properties of several typical 2D materials, including graphene, silicene and MoS2 monolayer upon lithium intercalation were studied, based on the density functional theory calculations with the model developed by Topsakal and Ciraci (Appl Phys Lett 96:091912, 2010). It was found that the in-plane stiffness of 2D materials decreases with increases of lithium concentration. In-plane stiffness decreased about 9.8% at lithium concentration of 0.184 Li/A2 for graphene and 6.0% at a concentration of 0.153 Li/A2 for silicene. The evolution of in-plane stiffness of MoS2 monolayer as a function of lithium concentration and electron-doping concentration were compared. The in-plane stiffness of MoS2 monolayer decreased with increases of Li and electron concentration, which revealed that the electron doping effect is the mechanism causing the decrease of the mechanical stability of electrode materials upon lithiation.