Preparation and characterization of fast ion conducting lithium thio-germanate thin-films grown by RF magnetron sputtering

In this study, amorphous lithium thio-germanate thin-films were prepared as electrolytes for lithium rechargeable batteries by RF sputtering deposition in Ar atmospheres. For the first time, new high quality lithium germanium sulfide, nLi₂S + GeS₂(n = 1, 2, and 3) thin-films have been successfully made by RF sputtering and synthesized as new solid state electrolytes. Although these materials are unstable in air the starting materials, target materials, and thin-films were thoroughly characterized by XRD, Raman, SEM, XPS, and impedance spectroscopy using special setups to prevent contamination. Thin-films did not show any cracks and pits on the surface and the ionic conductivities of the thin-films are ∼1000 times higher than reported values for oxide thin-films. In this way, this work may provide a new way for developing new thin-film electrolytes for solid state lithium ion batteries.