A compact cell for electrochemical investigations of solid-state materials

Solid electrolytes are a key feature of all-solid-state batteries, which represent advanced energy storage systems. The investigation of electrochemical properties of promising materials is essential for the development of new compounds. Herein, we report a simple and compact polyether ether ketone (PEEK)-based cell for the analysis of air and moisture sensitive solid electrolytes, including brittle microcrystalline powders or tapes. The cell exhibits low intrinsic capacitance, enabling impedance spectroscopy across the full frequency range without interfering features and applicable for a large temperature range from −70 °C to 80 °C. Controlled fabrication and measurement pressures improve the reproducibility of impedance measurements. Using polytetrafluoroethylene samples of varying thickness, this stray capacitance is measured and determined. Temperature-dependent electrochemical impedance spectroscopy of Li₆PS₅Cl/hydrogenated nitrile butadiene rubber (HNBR) sheets, conducted between −70 °C and 80 °C, demonstrates the cell durability and the high reproducibility of impedance measurements. Furthermore, the airtightness and experimental consistency were maintained even after 250 h of operation. Finally, we highlight the importance of low intrinsic capacitance by successfully resolving the bulk and grain contributions in Li₆PS₅Cl.