Amorphous LiLaTiO₃as Solid Electrolyte Material

Abstract

Amorphous lithium lanthanum titanate (LLTO) thin films were successfully prepared by a sol-gel method with an all-alkoxide based route. The thin film resistance was determined from the complex spectra by fitting experimental data to the equivalent circuit. The ionic conductivities of amorphous LLTO thin films were 4.5 × 10−6, 6.9 × 10−6, 1.3 × 10−5, and 3.8 × 10−5 S/cm at 30°C, 50°C, 70°C, and 90°C, respectively. The activation energy of lithium ion conduction in the thin film was evaluated to be 0.36 eV in the temperature range of 30–90°C. The structure of amorphous LLTO was predicted by the ab-initio molecular dynamics (AIMD) simulations and analyzed by partial pair distribution functions, coordination numbers and Voronoi tessellation. It is observed that the local environment of Ti in amorphous LLTO is quite similar to that in the crystal state but the atomic packing is much less dense. The ionic diffusivities were derived from the mean square displacement curves and the conductivities were evaluated from the Nernst-Einstein's relation, showing good agreement with experimental data. The good ionic conductivity of amorphous LLTO is attributed to its open and disordered structure with large excessive volumes.