Elastic softening of group IVA (Si, Ge and Sn) materials by electron and lithium doping

摘要

Mechanically stable electrode materials are very important for the safety of the development of lithium ion batteries (LIBs). Group IVA (Si, Ge and Sn) based materials have emerged as alternative anode materials for LIBs with high storage capacity. In this work, the mechanical stability of group IVA (Si, Ge and Sn) materials after Li insertion was investigated using density functional theory. The results of Li insertion and electron doping into group IVA (Si, Ge and Sn) materials were compared. It was shown that both Li insertion and electron doping lead to significant volume expansion and elastic softening, the elastic constants C-11 and C-44 decrease with the increase of Li and electron concentration. A brittle to ductile transition occurs in Si and Ge materials by electron and Li doping. The results reveal the mechanism of the decrease of mechanical stability of group IV materials upon lithiation is due to the electron-doping effect.