First principles studies of silicon as a negative electrode material for lithium-ion batteries

An investigation of Li–Si alloys using density functional theory is presented. Various calculation methods and pseudopotentials are analyzed to best reproduce the potential versus composition curve of a Li/Li x Si electrochemical cell at high temperature using the experimentally observed Li–Si phases. Total energy calculations, structural optimizations, and bulk modulus estimations were completed for the Si, Li 12 Si 7 , Li 7 Si 3 , Li 13 Si 4 , Li 15 Si 4 , Li 22 Si 5 , and Li phases. The potential plateaus of the co-existing phase regions, obtained using the projector augmented wave (PAW) method, have an average absolute error of 31 mV with respect to experiment. The Li 7 Si 3 and Li 15 Si 4 compositions are discussed and the Li 15 Si 4 phase is found to have a lower bulk modulus relative to the other phases.