Optimizing Li+ conductivity in a garnet framework

Abstract

The garnet-related oxides with the general formula Li_7−xLa₃Zr_2−xTa_xO₁₂ (0 ≤ x ≤ 1) were prepared by conventional solid-state reaction. X-ray diffraction (XRD), neutron diffraction and AC impedance were used to determine phase formation and the lithium-ion conductivity. The lattice parameter of Li_7−xLa₃Zr_2−xTa_xO₁₂ decreased linearly with increasing x. Optimum Li-ion conductivity in the Li-ion garnets Li_7−xLa₃Zr_2−xTa_xO₁₂ is found in the range 0.4 ≤ x ≤ 0.6 for samples fired at 1140 °C in an alumina crucible. A room-temperature σ_Li ≈ 1.0 × 10⁻³ S cm⁻¹ for x = 0.6 with an activation energy of 0.35 eV in the temperature range of 298–430 K makes this Li-ion solid electrolyte attractive for a new family of Li-ion rechargeable batteries.