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

Highly ion-conductive thin films in the pseudobinary system Li4GeS4-Li3PS4 were prepared by pulsed laser deposition (PLD). Raman spectra showed that the obtained thin films were mainly composed of Li+, (PS4)(3-), (GeS4)(4-) and (GeS1/2S3)(3-) ions. The 33Li(4)GeS(4)center dot 67Li(3)PS(4) (mol%) thin film showed glass transition phenomenon at about 160 degrees 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 x 10(14) to 1.8 x 10(-3) S cm(-1) at 25 degrees 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. (C) 2014 The Ceramic Society of Japan. All rights reserved.