Structure Prediction of Li-Sn and Li-Sb Intermetallics for Lithium-Ion Batteries Anodes

A variety of new stable and metastable Li-Sn and Li-Sb intermetallics are presented using the ab initio random structure searching (AIRSS) and species swapping methods. These include LiSn₂-P4/mmm, Li₂Sn₃-P1, Li₇Sn₉-P4₂/n, Li₃Sn₂-P2₁/m, Li₅Sn₃-Im3m, Li₂Sn-Cmcm, Li₈Sn₃-R3m, Li₃Sn-P3₂, Li₇Sn₂- P1, Li₄Sn-P2₁, Li₅Sn-P6/mmm, Li₇Sn-Fmmm, LiSb-P4/mmm, Li₈Sb₅-Fd3m, Li₈Sb₃-P2/c, Li₄Sb-C2/m, Li₉Sb₂-P3m₁, Li₅Sb-P6/mmm, Li₆Sb-R3m, Li₈Sb-Pc, and Li₉Sb-Cmcm. The Li-Sn theoretical voltage curve was calculated to high accuracy mainly from experimentally known structures and shows excellent agreement with experimental electrochemical cycling measurements previously reported. Li₂Sn was found on the convex hull to within density-functional theory accuracy, and its mechanical stability was investigated by calculating the density of states of the phonon spectrum. The new structures obtained by AIRSS show a consistent structural evolution of Li-Sn phases as Li concentration is increased. First-principles NMR calculations on the hexagonal and cubic Li₃Sb phases are performed. Our NMR results are compared to findings of Johnston et al. (Chem. Mater. 2016, 28, 4032) and proposed as a diagnostic tool to interpret experimental data.