Cycle stability increase by insertion of Li-La-Ta-O thin-film electrolyte between cathode and solid electrolyte for all-solid-state battery

Recently, all‐solid-state batteries (ASSBs) with an inorganic solid electrolyte have attracted significant interest because of their high potential for unique applications in space, deep sea, and radioactive environments. The inorganic solid electrolyte is one of the most fundamental parts since it determines the C rate and self-discharge properties. We prepared a series of ASSBs based on lithium lanthanum tantalum oxide (LLTO) solid-electrolyte thin films with thicknesses of 0, 100, and 200 nm by radio frequency (RF) magnetron sputtering. The microstructure and composition of the LLTO thin films were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results show that the LLTO thin films have a high ionic conductivity, and they reduce the contact resistance between the cathode and the solid electrolyte, and increase the ion path between the cathode and the bulk electrolyte. Thus, they can be applied to ASSBs as an interlayer between the cathode and the solid electrolyte.