Sputter deposited Li7La3Zr2O$_{12}$ as electrolyte for thin film cells

Most commercial state-of-the-art batteries work with a liquid organic electrolyte which might cause safety problems due to an insufficient thermal and electrochemical stability. Replacing the liquid by a solid electrolyte is one approach to overcome these problems. Next to sulfides and phosphates, oxide compounds like the garnet-structured Li7La3Zr2O12 (LLZ) are promising materials for solid electrolytes. LLZ exists in two modifications, a tetragonal and a cubic, whereby the cubic high temperature phase shows a higher Li-ion conductivity (about 10-4 S/cm). Further advantageous properties of LLZ are its thermal (up to 1050°C) and electrochemical stability (up to 8V) which allows its usage with high-voltage electrodes or in batteries at elevated temperatures. Since the conductivity is two orders of magnitude lower compared to organic electrolytes the overall resistance can be lowered by reduction to a thin electrolyte layer in all-solid-state cells.R.f. magnetron sputter deposition is one approach to coat large substrate areas with LLZ electrolyte. In order to get crack-free, dense and single phase LLZ thin films, deposition parameters need to be adjusted carefully, which is shown by x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM). In our study conductivities up to 10-6 S/cm are achieved for single phase cubic thin films. Furthermore, LLZ thin films were successfully integrated into all solid state cells, which are also characterized