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

Abstract

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.