Lithium diffusion in silicon and induced structure disorder: A molecular dynamics study

Abstract

Using molecular dynamics method, we investigate the diffusion property of lithium in different silicon structures and silicon structure's disorder extent during lithium's diffusion process. We find that the pathway and the incident angle between the direction of barrier and diffusion of lithium are also the essential factors to the lithium's diffusion property in silicon anode besides the barrier. Smaller incident angle could decrease the scattering of lithium in silicon structure effectively. Moreover, lithium diffuses easier in the Li-Si alloy structure of higher lithium concentration with deeper injection depth. The silicon's structure will be damaged gradually during the charge and discharge process. However, it will also recover to initial state to a great extent after relaxation. Therefore, the damage of lithium diffusion to silicon anode in the structure of low lithium concentration is reversible to a great degree. In addition, the silicon structure of <110> crystal orientation perform better properties in both lithium's diffusivity and structural stability.