Development of thin-film solid electrolyte-electrode system for all-solid-state applications

All-solid-state batteries have been shown as an innovative candidate for next-gen lithium-ion batteries. Thin-film technologies offer an approach to solve several inherent challenges. To achieve a complete thin-film all-solid-state battery all components, especially electrodes and solid electrolytes have to be prepared in a suitable combination. In contrast to conventional liquid-solid electrolyte-electrode systems, additional requirements arise from the fact that electrochemically active interfaces have to be formed while preparing. Using cost efficient and upscalable sol-gel processes solid NASICON-type electrolytes (e. g. Li1+xAlxTi2-x(PO4)3, LATP) offer a high ionic conductivity at room temperature and a high anodic stability [1]. In previous work we presented a LATP solid electrolyte prepared by sol-gel methods on a current collector as substrate [2]. In a layer-by-layer setup (shown in Fig. 1) the substrate-anode system forms the underlying substrate for the electrolyte coating. Oxide-based electrodes indicate interfacial reactions in the presence of NASICON-type electrolytes at temperatures higher than 300 °C [3]. Therefore they turned out to be unstable in the coating-associated temperature treatment. Phosphate-based electrode materials provide a suitable approach. This poster presents single- and multi-layer films a of phosphate-based anode material on conducting transparent oxides prepared by dip- and spin- coating method. The single- and multi-layer systems exhibited good electrochemical properties and appear suitable for the electrolyte coating process including the associated temperature treatment. Grazing incidence X-ray diffraction reveals no interface reaction and SEM investigation shows a good physical connection on the electrolyte-electrode interface. Furthermore, half-cell CV and cycling tests confirm a low charge transfer resistance at the interface. Future work will focus on the cathode/electrolyte interface and finally a working solid-state cell.