Ionic Transport in Potential Coating Materials for Mg Batteries

TL;DR

This study uses computational methods to identify promising Mg-containing coating materials that facilitate ion transport and enhance the stability of magnesium batteries with different electrode types.

Contribution

It introduces a systematic computational approach to evaluate Mg transport in various compounds, identifying new potential coating materials for Mg batteries.

Findings

MgSiN₂, MgI₂, MgBr₂, MgSe, MgS as coatings against Mg metal anode.

MgAl₂O₄ and Mg(PO₃)₂ as cathode coatings up to 3V.

Identification of compounds with low Mg migration barriers.

Abstract

A major bottleneck for the development of Mg batteries is the identification of liquid electrolytes that are simultaneously compatible with the Mg-metal anode and high-voltage cathodes. One strategy to widen the stability windows of current non-aqueous electrolytes is to introduce protective coating materials at the electrodes, where coating materials are required to exhibit swift Mg transport. In this work, we use a combination of first-principles calculations and ion-transport theory to evaluate the migration barriers for nearly 27 Mg-containing binary, ternary, and quaternary compounds spanning a wide chemical space. Combining mobility, electronic band gaps, and stability requirements, we identify MgSiN$_2$, MgI$_2$, MgBr$_2$, MgSe, and MgS as potential coating materials against the highly reductive Mg metal anode, and we find MgAl$_2$O$_4$ and Mg(PO$_3$)$_2$ to be promising materials against high-voltage oxide cathodes (up to $\sim$3~V).