Crystalline lithium silicides Li _x Si _y are a group of Zintl-like compounds, of which Li _15 Si _4 is observed crystallizing in Si anodes after complete electrochemical lithiation. Here, Li diffusion in Li _1 Si _1 , Li _12 Si _7 , Li _13 Si _4 and Li _15 Si _4 is extensively studied by means of ab initio molecular dynamics simulations and nudged elastic band calculations considering various intrinsic point defects. Li interstitials are identified as the main vehicle of diffusion due to typically low formation and migration energies. They diffuse via an interstitialcy mechanism usually involving 2 or 3 atoms. Moreover, Frenkel defects are found to play a role in Li _12 Si _7 and Li _13 Si _4 only, as their formation energies are relatively high in Li _1 Si _1 and Li _15 Si _4 . All investigated intrinsic defects have an impact on energy barriers of nearby as well as farther diffusion paths.
