Influence of inversion on Mg mobility and electrochemistry in spinels

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${}^{2+}$ ionic mobility in MgMn${}_2$O${}_4$ as a prototypical cathode, and MgIn${}_2$S${}_4$ 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${}^{2+}$ migration barriers, along specific migration pathways, in the oxide as well as the sulfide. To quantify the impact of spinel inversion on macroscopic Mg${}^{2+}$ transport, we determine the percolation thresholds in both MgMn${}_2$O${}_4$ and MgIn${}_2$S${}_4$. Furthermore, we analyze the impact of inversion on the electrochemical properties of the MgMn${}_2$O${}_4$ 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.

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Cited by in corpus (7)

• Evaluating transition-metal oxides within DFT-SCAN and SCAN+U frameworks for solar thermochemical applications
• Role of point defects in spinel Mg chalcogenide conductors
• On the Balance of Intercalation and Conversion Reactions in Battery Cathodes
• Evaluation of Mg compounds as coating materials in Mg batteries
• Exploration of amorphous V${}_2$O${}_5$ as cathode for magnesium batteries
• Leveraging transfer learning for accurate estimation of ionic migration barriers in solids
• Ionic Transport in Potential Coating Materials for Mg Batteries