Tetra-butyl ammonium fluoride – An advanced activator of aluminum surfaces in organic electrolytes for aluminum-air batteries

This study reports an innovative Al-air battery system utilizing new organic non-aqueous electrolytes. The Al surface activating electrolytes involved tetra-butylammonium fluoride tri-hydrate (TBAF∙3H₂O) salt dissolved in different “traditional” non-aqueous battery solvents, such as propylene carbonate (PC), tetra-ethylene glycol dimethyl ether (TEG-DME), acetonitrile (ACN) and dimethyl sulfoxide (DMSO). Conductivity and activation energy evaluations of the different electrolytes are reported alongside electrochemical measurements and surface characterization, using high-resolution scanning electron microscopy (HR-SEM). This study concludes that the most successful activation of the aluminum surface is obtained with the use of an electrolyte consisting of 1 M of TBAF tri-hydrate salt in PC, resulting in high anodic currents. The active species present in the electrolyte were detected and analyzed with the use of an Attenuated Total Reflection Fourier Transform Infra-Red (ATR-FTIR) spectroscopy method. The X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) measurements are indicative of the formation of an active, and yet protective fluoride containing layer, once the Al surface is exposed to the electrolyte media. Half-cell and primary Al-air cells evaluation with the use of different discharge anodic currents were performed utilizing various TBAF tri-hydrate salt concentrations dissolved in the organic solvent. The promising results achieved in this study constitute a foundation for future electrolyte solutions developed for Al-air battery systems.