Sol–gel-processed amorphous inorganic lithium ion electrolyte thin films: sol chemistry

Abstract

Amorphous lithium lanthanum titanium oxide (LLTO) is a promising inorganic solid electrolyte for all-solid-state lithium ion batteries. Preparation of amorphous LLTO using a sol–gel process has been reported. Sol chemistry is vital. In this study, two different sol synthetic strategies, all-alkoxide and acetate–alkoxide routes, were employed to prepare amorphous LLTO thin films. XRD and TEM results show that thin films derived from these two routes are amorphous. SEM results indicate that these thin films are dense and crack-free, but there are differences in their surface morphology. The ionic transport properties of the thin films were measured. The ionic conductivity of the thin film from the all-alkoxide route is almost two orders higher than that from the acetate–alkoxide route. This striking difference results from different sol chemistries. The value 0.36 eV was determined as the activation energy of lithium ion conduction in the thin film from the all-alkoxide route in the temperature range 30–90 °C.