In search of high performance anode materials for Mg batteries: Computational studies of Mg in Ge, Si, and Sn

We present ab initio studies of structures, energetics, and diffusion properties of Mg in bulk Si, Ge, and Sn diamond structures to evaluate their potential as insertion type anode materials for Mg batteries. We show that Si could provide the highest specific capacity (3817 mAh g(-1)) and the lowest average insertion voltage (similar to 0.15 eV vs. Mg) for Mg storage. Nevertheless, due to its significant percent lattice expansion (similar to 216%) and slow Mg diffusion, Sn and Ge are more attractive; both anodes have lower lattice expansions (similar to 120% and similar to 178%, respectively) and diffusion barriers (similar to 0.50 and similar to 0.70 eV, respectively, for single-Mg diffusion) than Si. We show that Mg Mg interactions at different stages of charging can decrease significantly the diffusion barrier compared to the single atom diffusion, by up to 0.55 eV. (C) 2013 Elsevier B.V. All rights reserved.