Theoretical study of [111]-germanium nanowires as anode materials in rechargeable batteries: a density functional theory approach

In this work, we present a Density Functional Theory (DFT) study of hydrogen-passivated germanium nanowires grown along the [111] crystallographic direction. The study is performed within the local density approximation (LDA) and the supercell technique. Four different diameters of nanowires were considered and the surface hydrogen atoms were replaced by Li ones using a sequential process. The results indicate that the nanowires have a semiconductor behaviour and the energy band gap diminishes when the number of Li atoms per unit cell increases. The formation energy results reveal that the Li atoms increase the stability of the Ge nanowires, and there is a charge transfer from the Li atoms to the surface Ge atoms. The open circuit voltage values are almost independent of the concentration of Li atoms. On the other hand, the lithium storage capacity results reveal that the Ge nanowires could be good candidates to be incorporated as anodic materials in the new generation of rechargeable batteries.