Composition Dependence of Lithium Diffusion in Lithium Silicide: A Density Functional Theory Study

Abstract The lithiation process of silicon was investigated by using ab initio molecular dynamics. Diffusion coefficients of Li in Li–Si alloys were calculated to be in the range between 2.08×10 −9 and 3.53×10 −7 cm 2 s −1 at room temperature. The results showed that the Li mobility is strongly dependent on the composition of the Li x Si alloys. The Li diffusivity in a Li x Si alloy can be enhanced by two orders of magnitude when x is increased from 1.0 to 3.75, which can be explained by the instability of the Si network, owing to charge transfer from Li to Si.