Systematic Study of Aluminum Corrosion in Ionic Liquid Electrolytes for Sodium-Ion Batteries: Impact of Temperature and Concentration

Thedevelopment of sodium-ion batteries utilizing sulfonylamide-basedelectrolytes is significantly encumbered by the corrosion of the Alcurrent collector, resulting in capacity loss and poor cycling stability.While ionic liquid electrolytes have been reported to suppress Alcorrosion, a recent study found that pitting corrosion occurs evenwhen ionic liquids are employed. This study investigates the effectsof temperature and Na salt concentration on the Al corrosion behaviorin different sulfonylamide-based ionic liquid electrolytes for sodium-ionbatteries. In the present work, cyclic voltammetry measurements andscanning electron microscopy showed that severe Al corrosion occurredin ionic liquids at high temperatures and low salt concentrations.X-ray photoelectron spectroscopy was employed to identify the differentelemental components and verify the thickness of the passivation layerformed under varied salt concentrations and temperatures. The differencesin the corrosion behaviors observed under the various conditions areascribed to the ratio of free [FSA](-) to Na+-coordinating [FSA](-) in the electrolyte and thestability of the newly formed passivation layer. This work aims ataugmenting the understanding of Al corrosion behavior in ionic liquidelectrolytes to develop advanced batteries.