Novel Mg-ion conductive oxide of μ-cordierite Mg_0.6Al_1.2Si_1.8O₆

Solid electrolytes with high Mg-ion conductivity are required to develop solid-state Mg-ion batteries. The migration energies of the Mg²⁺ ions of 5,576 Mg compounds tabulated from the inorganic crystal structure database (ICSD) were evaluated via high-throughput calculations. Among the computational results, we focused on the Mg²⁺ ion diffusion in Mg_0.6Al_1.2 Si_1.8O₆, as this material showed a relatively low migration energy for Mg²⁺ and was composed solely of ubiquitous elements. Furthermore, first-principles molecular dynamics calculations confirmed a single-phase Mg²⁺ ion conductor. The bulk material with a single Mg_0.6Al_1.2Si_1.8O₆ phase was successfully prepared using the sol-gel method. The relative density of the sample was 81%. AC impedance measurements indicated an electrical conductivity of 1.6 × 10^-6 Scm^-1 at 500°C. The activation energy was 1.32 eV, which is comparable to that of monoclinic-type Mg_0.5Zr₂(PO₄)₃.