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

TL;DR

This study uses computational methods to evaluate Mg insertion in Si, Ge, and Sn as potential anode materials for Mg batteries, highlighting trade-offs between capacity, voltage, and diffusion properties.

Contribution

It provides a comparative analysis of Mg diffusion and capacity in Si, Ge, and Sn, identifying Sn and Ge as more practical anode candidates due to lower lattice expansion and diffusion barriers.

Findings

Si offers highest capacity and lowest insertion voltage.

Sn and Ge exhibit lower lattice expansion and diffusion barriers.

Mg-Mg interactions can significantly reduce diffusion barriers.

Abstract

We present ab initio studies of structures, energetics, and diffusion properties of Mg in 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 capacities (3817 mAh g-1) and the lowest average insertion voltage (~0.15 eV vs. Mg) for Mg storage. Nevertheless, due to its significant percent lattice expansion (~216%) and slow Mg diffusion, Sn and Ge are more attractive; both anodes have lower lattice expansions (~120 % and ~178 %, respectively) and diffusion barriers (~0.50 and ~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.