Dual-electrolyte system for suppressing corrosion of aluminum electrode in aluminum-air flow battery

Abstract

Aluminum-air batteries have received considerable attention as an electrical power source due to their theoretical specific capacity reaching 2.98 Ah/g. Further, Al-air batteries are abundant and low cost. On the other hand, the aluminum in the batteries has a problem, such that it is subject to self-corrosion in alkaline. Herein, this work concentrates on the aluminum’s corrosive behavior and self-corrosion in methanol-3M KOH mixed solution containing different percentages of deionized water i.e. (0, 5, 10 and 20)%wt, using electrochemical (half-cell testing). The aluminum-air battery consists of: aluminum anode | anolyte | anion exchange membrane | catholyte | air cathode. The anolyte is the methanol-based electrolyte, and the catholyte is a gel polymer electrolyte. As regards the half-cell, the increase in water reduced the inner surface layer between the aluminum film and electrolyte. Simultaneously, the increase in water reduced the overpotential required and generated faster reaction. However, much more hydrogen gas was produced along with self-corrosion. The Al-air battery was examined when discharging at 10 mA/cm2. At the condition 0%water, the highest specific capacity reached 2328 mAh/g and utilization 78%. When water was increased, the specific capacity declined significantly due to self-corrosion of the aluminum. Besides, the flow rates of the electrolyte were adjusted; average voltage was higher when the flow rate of the electrolyte was increased.