Hybrid Ionic Liquid Propylene Carbonate-Based Electrolytes for Aluminum-Air Batteries

This study reports on the use of tetrabutylammonium dihydrogen trifluoride (TBAH₂F₃) ionic liquid-based electrolytes in the aluminum (Al)-air battery system. The conductivity and activation energy of the electrolytes are reported alongside with electrochemical measurements and Al surface characterizations. The activation process of the Al surface is demonstrated and monitored in the ionic liquid-based electrolyte. The successful activation of the Al surface is obtained via the action of the H₂F₃ ^- species present in the ionic liquid. The active species in the electrolyte are analyzed with the use of an attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method, applied prior and subsequent to cell discharge. Primary Al-air cell evaluations with the use of different anodic discharge current loads, as well as different volume fractions of propylene carbonate (PC), were conducted. Using the electrochemical impedance spectroscopy (EIS) technique, we were able to monitor the wetting process of the air cathode. The use of TBAH₂F₃-based electrolytes resulted in high cell capacities (over 70% of the theoretical value). The results achieved and reported in this study are promising and present an additional option for an ionic liquid-based electrolyte for Al-air batteries.