Amorphous and perovskite Li3xLa(2/3)-xTiO3 (LLT) solid electrolyte for all-solid-state lithium-ion batteries

Abstract

In order to tackle the challenging energy storage problem, Lithium-ion (Li-ion) batteries are promising candidates due to their high power and energy density. However, lifetimes and safety of contemporary batteries are limited due to the use of a liquid electrolyte. All-solid-state Li-ion batteries, where liquid electrolyte is replaced by introducing a solid electrolyte such as LLT, could circumvent these issues. Although a lot is known about LLT powders, little is known about (thin) films of this material. In this study, thin films of LLT have been deposited by spin coating on TiO2 as an anode. An aqueous citrate / nitrate precursor solution was synthetized. Thermal analysis showed decomposition of the precursors was completed by 600°C. in-situ XRD studies of the LLT thin film crystallization, indicated that prolonged heating at 700 °C was required to obtain tetragonal Perovskite LLT on TiO2. SEM and ATR-FTIR showed that dense thin films with thicknesses ranging from 50 to 400 nm have been formed with negligible organic contents. Finally, the ion conductivity of the amorphous LLT film was assessed by impedance spectroscopy, indicating a Li-ion conductivity in the range of 10-8 S/cm. Although the conductivity should be further improved, this study indicates that aqueous CSD is a promising route for preparing Li0.35La0.55TiO3 solid Li-ion conductor compared to other deposition methods.