Novel Aluminum Air Ionic Liquid Based Battery

The changing and expanding needs in the energy market, ranging from power grid energy storage systems to portable power sources, dictates the development of efficient, inexpensive, and high performance battery systems. These advanced electrochemical systems should better deal with the challenges posed by the nascent green economy and non-oil based transport systems. One of the promising avenues for achieving these goals is the development of battery systems based on aluminum (Al) and its alloys as anodes. The main advantages of such systems are the low equivalent weight of Al, its high natural abundance in the earth’s crust, (leading to a rather low price), and its safety characteristics. In addition, Al and its by-products are non-toxic and environmental friendly. Aluminum battery systems cover a wide range of applications; from field-portable emergency power supply to remote power applications and batteries for transportation. Theoretically Al contains approximately one-half the energy content of gasoline per unit weight (8,100 Wh/kg for Al-air and 13,000 Wh/kg for gasoline) and three times the energy per unit volume (21,870 Wh/l for Al-air  and  9,700 Wh/l for gasoline). Currently, the best practical utilization of gasoline for automotive applications can reach approximately 1,700 Wh/Kg and for aqueous Al-air batteries the values are 300-500 Wh/Kg. Nevertheless, the utilization of Al-air batteries as a sustainable energy storage device is hampered by some severe problems. High corrosion rate of the Al anode in aqueous alkaline solution is of great concern in terms of Al utilization and safety. On the other hand, Al surface activation is somewhat problematic in non-aqueous electrolytes, limiting substantially the possibility to utilize any power output. In this study, a newly developed non-aqueous Al-air battery is presented. The battery configuration utilizes 1-ethyl-3-methylimidazolium oligo-fluoro-hydrogenate (EMIm(HF)_2.3F) room temperature ionic liquid (RTIL). The battery shows the ability to sustain current densities up to 1.5 mA/cm², producing a capacity of 140 mAh/cm² and thus, utilizing above 70% of the theoretical Al capacity. This is equivalent to an outstanding energy densities of 2,300 Wh/Kg and 6,200 Wh/L. Al₂O₃is detected at the air electrode as the battery discharge product, being the main cathodic reaction of oxygen reduction coupled with Al ions migrated to the air electrode.

* Equally contributed to the presented study