Elastic properties of crystalline Li-Ge phases with increasing Li concentration: A first-principles study

To obtain a better understanding of the failure mechanism of Ge anode during the charging and discharging process, in this paper, we systematically studied the mechanical properties of Li-Ge alloys based on density functional theory. The results show that the bulk, shear, and Young's moduli of Li-Ge alloys decrease almost linearly with increasing Li concentration. In addition, based on the analysis of shear to bulk modulus and Poisson's ratios, Li Ge alloys demonstrate enhanced brittleness during the lithiation process which would make electrode materials fragile to cracks and failure. The weakened elastic moduli and enhanced brittleness would lead to the poor cycle performance and crushing failure of Ge anode materials during charging and discharging process. (C) 2018 Author(s).