Electrochemical Characterization of a Drawn Thin-Film Glassy Mixed Oxy-Sulfide-Nitride Phosphate Electrolyte Material for Applications in Solid-State Batteries

Abstract

Thin-film glassy solid-state electrolytes are often considered for applications in energy storage devices; fully-dense thin-film glassy electrolyte materials are able to minimize power loss while suppressing dendrite growth. The glass with the composition Na4P2S5.8O0.92N0.18 (NaPSON) was chosen because it balances the high conductivity of a sulfide chemistry with the high processability and electrochemical stability of an oxy-nitride chemistry. NaPSON thin-film glassy solid-state electrolyte ribbons with thicknesses that range from 75 to 600 μm were drawn using a process of softening and drawing of a cast and annealed preform. Raman spectroscopy was run on the thin-film samples to ensure the material was structurally similar after processing across different thicknesses and remelts. Electrochemical impedance spectroscopy (EIS) was used on varying thicknesses of thin-film to investigate and compare the ionic conductivity of Na+ in the thin film compared to the bulk sample. Area specific resistance models as a function of time were created to compare the trend of bulk and interfacial resistances of different thicknesses. Thin-film samples were made into symmetric cells and cycled. The cycling of the symmetric cells gave insight into the behavior and durability of the electrolyte under applied voltage and sustained current. These results show that drawn thin-film electrolytes are a solid research direction.