Mechanism of Li intercalation into Si

Using density functional theory calculations, we study intercalation of Li into Si via Si(100) and (111) surfaces. We find that in contact with Li atoms, the surfaces are covered with a high coverage of Li adatoms. Insertion of Li into Si only takes place from (100) surface via a pushing mechanism. In this mechanism, Li atoms that have already adsorbed on the (100) surface are repelled by nearly adsorbed Li atoms and pushed down to penetrate into the subsurface. This mechanism is not possible on Si(111) on which the adsorbed Li atoms block the penetration of Li atoms. Since Si is a promising candidate to replace the graphite in Li-ion batteries, the present work can help us to better understand the process of Li insertion and extraction in Si anode materials of future batteries. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794825]