Influence of lithium concentration on the structure and Li+ transport properties of cubic phase lithium garnets

Abstract

To understand the influence of lithium concentration on the structure and Li⁺ transport properties of cubic lithium garnets, systematic AC impedance, Raman and powder X-ray diffraction (PXRD) investigations have been carried out on lithium garnets with nominal compositions Li_xA₃B₂O₁₂ (A = Y³⁺, La³⁺, Sr²⁺, Ba²⁺; B = Te⁶⁺, Ta⁵⁺, Zr⁴⁺ and 3 ≤ x ≤ 7.5). The size of the three dimensional A₃B₂O₁₂ frame is found to be an important factor in determining the capacity of housing and the nature of distribution of lithium atoms among available tetrahedral and octahedral sites in the cubic Li_xA₃B₂O₁₂ lithium garnets. The Li⁺ conduction in a cubic phase lithium garnet is primarily dependent upon the concentration of lithium and the nature of distribution of lithium atoms among tetrahedral and octahedral sites. AC impedance analysis of cubic phase Li_xA₃B₂O₁₂ revealed an increase in the hopping of Li⁺ with the increase in Li⁺ concentration, reaches a maximized value for the nominal composition Li₇La₃Zr₂O₁₂ and then decreases with the further increase of lithium concentration.