Enhancing the efficiency of Li-ion Batteries by modifying the Solid Garnet Electrolytes

Abstract

Lithium garnet oxides are highly considered as very promising solid electrolyte candidates for all-solid-state lithium ion batteries (SSLiBs). My thesis’s goal is to explore new garnet electrolyte materials by tuning the substitution in the frame structure. A systematic study on lithium-stuffed garnet-type Li5+2xLa3Ta2-xMxO12 (M= Sm, Gd; 0 ≤ x ≤ 0.55) has been carried out to understand the effect of both Gd, Sm - and Li- content on the structural, electrical, physical, chemical and electrochemical properties. The results from Powder X-ray diffraction (PXRD) and Scanning Electron Microscopy (SEM) suggested structural and morphological transformation as a function of dopant concentration. PXRD studies have revealed the cubic garnet-type structure of the materials with space group Ia-3d, and also have proved that the lattice parameter increases with an increase in Sm, Gd, and Li-content. The AC electrochemical impedance spectroscopy (EIS) has shown that the sample with 0.35 doping percent is the best Li+ ion conductor, with a conductivity of 2.25 x 10-5 and 8.18x10-5 Scm-1 at room temperature for Sm and Gd-doped samples, respectively. Evaluation of dielectric properties of Li5+2xLa3Ta2-xMxO12 (M= Sm, Gd; 0 ≤ x ≤ 0.55) has been carried out by employing AC EIS method. In addition, the dielectric properties were also investigated in the light of electron energy loss functions, which showed some surface energy loss function (SELF) and negligible volume energy loss function (VELF) for the studied garnets. Surface and volu