Influence of inversion on Mg mobility and electrochemistry in spinels
arXiv:1708.07458 · doi:10.1021/acs.chemmater.7b02820
Abstract
Magnesium oxide and sulfide spinels have recently attracted interest as cathode and electrolyte materials for energy-dense Mg batteries, but their observed electrochemical performance depends strongly on synthesis conditions. Using first principles calculations and percolation theory, we explore the extent to which spinel inversion influences Mg ionic mobility in MgMnO as a prototypical cathode, and MgInS as a potential solid electrolyte. We find that spinel inversion and the resulting changes of the local cation ordering give rise to both increased and decreased Mg migration barriers, along specific migration pathways, in the oxide as well as the sulfide. To quantify the impact of spinel inversion on macroscopic Mg transport, we determine the percolation thresholds in both MgMnO and MgInS. Furthermore, we analyze the impact of inversion on the electrochemical properties of the MgMnO cathode via changes in the phase behavior, average Mg insertion voltages and extractable capacities, at varying degrees of inversion. Our results confirm that inversion is a major performance limiting factor of Mg spinels and that synthesis techniques or compositions that stabilize the well-ordered spinel structure are crucial for the success of Mg spinels in multivalent batteries.
References in corpus (5)
- Restoring the density-gradient expansion for exchange in solids and surfaces
- Generalized gradient approximation for solids and their surfaces
- The intercalation phase diagram of Mg in VO from first principles
- Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Non-Aqueous Electrolytes
- Impact of Intermediate Sites on Bulk Diffusion Barriers: Mg Intercalation in MgMoO