Structure, Ionic Conductivity, and Dielectric Properties of Li-Rich Garnet-type Li_5+2xLa₃Ta_2-xSm_xO₁₂ (0 ≤ x ≤ 0.55) and Their Chemical Stability

Lithium garnet oxides are considered as very promising solid electrolyte candidates for all-solid-state lithium ion batteries (SSLiBs). In this work, we present a cubic garnet-type Li_5+2xLa₃Ta_2-xSm_xO₁₂ (0 ≤ x ≤ 0.55) system as a potential electrolyte for SSLiBs. Powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) were employed to investigate the structural stability of Li_5+2xLa₃Ta_2-xSm_xO₁₂. The results from PXRD and SEM suggested structural and morphological transformation as a function of dopant concentration. In addition to Li-ion transport in Li_5+2xLa₃Ta_2-xSm_xO₁₂, the dielectric properties were also investigated in the light of electron energy loss functions, which showed some surface energy loss and negligible volume energy loss for the studied garnets. Surface and volume energy loss functions of a mixed conducting LiCoO₂ was studied for comparison. The long-term chemical stability of one of members, Li_5.3La₃Ta_1.85Sm_0.15O₁₂, was performed on aged sample using PXRD, SEM, and thermogravimetric analysis.