Li4GeS4-Li3PS4 electrolyte thin films with highly ion-conductive crystals prepared by pulsed laser deposition

Abstract

Highly ion-conductive thin films in the pseudobinary system Li 4GeS4-Li3PS4 were prepared by pulsed laser deposition (PLD). Raman spectra showed that the obtained thin films were mainly composed of Li+, (PS4)3-, (GeS 4)4- and (GeS1/2S3)3- ions. The 33Li4GeS4·67Li3PS4 (mol%) thin film showed glass transition phenomenon at about 160°C, suggesting that the obtained amorphous thin film was in a glassy state. The thin film exhibited higher ionic conductivity than the Li4GeS4 and Li3PS4 thin films because of the so-called "mixed anion effect". Furthermore, the structural rearrangement and crystallization after heat treatment for the thin film increased ionic conductivity from 1.1 § 10-4 to 1.8 § 10-3Scm-1 at 25°C, and decreased activation energy from 42 to 28 kJ mol-1. Highly lithium-ion conductive thin films prepared in this study are promising for the application to bulk-type all-solid-state lithium secondary batteries. © 2014 The Ceramic Society of Japan. All rights reserved.