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

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 x 10(-9) and 3.53 x 10(-7) cm(2) s(-1) at room temperature. The results showed that the Li mobility is strongly dependent on the composition of the LixSi alloys. The Li diffusivity in a LixSi 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.