Unraveling fundamental characteristics of Na2Mg3Cl8 as a solid-state electrolyte for Na-ion batteries

Abstract

In this theoretical study, we harnessed advanced atomistic computations to unravel several features of Na₂Mg₃Cl₈, an unexplored but promising chloride compound for solid-state electrolytes in Na-batteries. First, Na₂Mg₃Cl₈ exhibits an insulating behavior, characterized by an energy gap of ∼5 eV, arising from the hybridization of [NaCl] trigonal prismatic and [MgCl₆] octahedral units. Second, the compound possesses mechanical stability and ductility, which render it suitable for practical fabrication. Improved electrolyte/electrode contact can reduce resistance and enhance battery performance. The electrochemical performance of Na₂Mg₃Cl₈ involves an open cell voltage of 1.2 V and a theoretical capacity of 133 mA h g⁻¹. Finally, its transport characteristics include low activation energy for diffusion and conduction as well as a remarkable room-temperature conductivity of 1.26 mS cm⁻¹, comparable to those of current superionic conductors.