Prospects for Amorphous Na-GeSe Thin Film Applications in Solid-State Batteries*

The cost of lithium, its limited availability, and the flammability of current organic electrolytes present significant challenges for the future of rechargeable lithium-ion batteries in power storage applications. The growing demand for large-capacity rechargeable power storage devices in electric vehicles and robotics necessitates the development of safe, low-cost all-solid-state batteries to prevent leakage, volatilization, and flammability. Rechargeable sodium-ion batteries are promising candidates to meet these requirements, provided suitable materials for cathodes and solid-state electrolytes are identified. Germanium selenide glasses are potential candidates due to their wide glass-forming range, covalent bonding, and substantial free volume. In this study, amorphous thin films of sodium-containing germanium selenides were successfully prepared using thermal evaporation in a vacuum. These films were characterized using scanning electron microscopy and impedance spectroscopy. Electrical characterization was conducted over frequencies ranging from 4 Hz to 8 MHz using a HIOKI LCR meter and a temperature-controlled LINKAM stage. The temperature and frequency dependencies of the measured electrical parameters were used to calculate complex plane dependencies. The potential of this material as a solid-state electrolyte for sodium transport is discussed.