The solid electrolyte interface (SEI) plays an important role in battery performance with excessive growth resulting in battery failure. The SEI is thought to form from electrolyte decomposition beginning during the initial discharge of half-cell batteries and is affected by the presence of electrolyte additives. Herein, X-ray photoelectron spectroscopy (XPS) is used to analyze the SEI formed on electrodeposited Cu2Sb thin films in sodium ion half-cell batteries without interference from binders. The presence of fluoro-ethylene carbonate (FEC), an electrolyte additive known to enhance battery lifetime, is seen to have a significant effect on the carbon 1s XPS spectra on the Cu2Sb on differing potentials through the first discharge. SEI species were detected before the battery is cycled through a series of controlled experiments between sodium metal and battery electrolyte. The reactivity of sodium metal was determined to form the initial components of the SEI. FEC plays an important role in this reaction, changing what species are detected on the surface of the Cu2Sb. Further characterization of the sodium metal by XPS reveals the differing chemical environments that have a dramatic effect on battery performance. These results suggest that the critical aspects of SEI growth in sodium systems are determined before the active material is cycled, with FEC playing an integral role in determining how the SEI forms. This work demonstrates the critical importance of understanding and characterizing each variable in a complex system.

XPS characterization of sodium ion battery solid electrolyte interface formation: Understanding the role of fluoro ethylene carbonate

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.