Lithium-ion conductivity and crystal structure of garnet-type solid electrolyte Li_7−xLa₃Zr_2−xTa_xO₁₂ using single-crystal

Abstract

Single-crystal rods of Li_7−xLa₃Zr_2−xTa_xO₁₂ (X = 0.2, 0.4, 0.5, 0.6, 0.8) were grown by floating zone melting. The typical size of the single-crystal rod was 8 mm in diameter and 70 mm in length. Li_7−xLa₃Zr_2−xTa_xO₁₂ (X = 0.2, 0.4, 0.5, 0.6, 0.8) crystallizes in a cubic structure with an Ia-3d space group. Single crystal structure analysis was performed for all single crystals. How the lithium ion conductivity varies with the substitution amount of tantalum was investigated using a single crystal. Analyzing the results of AC impedance measurements, we estimated the total Li-ion conductivity of member in Li_7−xLa₃Zr_2−xTa_xO₁₂ single-crystal. As a result, when X = 0.4, the lithium ion conductivity became the maximum, and it was 1.10 × 10 ⁻³ S cm⁻¹ at 298 K. The activation energy ticked up with increasing tantalum substitution.