Formation of garnet-type Li7La3Zr2O12 nanoparticles as an alternative structural stabilization route

Abstract

The cubic garnet-type Li7La3Zr2O12 (LLZO) is an eminent candidate for next-generation solid state battery technology due to its therma stability and high ionic conductivity. As such, its operation mechanisms need to be thoroughly understood, particularly on the structural nstability challenge reported to occur at lower temperatures. Although it exists as either the tetragonal or cubic structures, the latter is favourable because of its higher Li+ conductivity rate. However, inability to retain thermodynamic stability in cubic phase at low temperatures (≤ 903,15 K) remains a challenge. As an alternative to extrinsic doping, as recently attempted in various studies, it has been discovered that decreasing the size to nano-level could remedy the phase stability challenge of cubic LLZO. Herein, we have modelled the bulk and nanostructured LLZO under various temperature conditions in the range 300 – 1500 K using the DL_ POLY molecular dynamics code, to understand the LLZO high temperature behaviour and track phase transformations. The molecular dynamics calculations performed on these materials revealed two distinct patterns of Li-ion transport on the diffusion coefficient plots. The trends in conductive ion diffusions show that nanostructured materials yield higher diffusion coefficients that the bulk structures. Findings of this study form a strong foundation towards the amorphization and recrystallization of these materials to monitor any change in structure post crystallization since the ability to retain both structural and conductivity rate are equally crucial.