Development of anodes for aluminium/air batteries ? solution phase inhibition of corrosion

Abstract

The discharge characteristics of aluminium in inhibited and uninhibited 4 M KOH at 50°C have been explored. The performance of pure aluminium as a fuel is compared with that for two leading alloy fuels that had been evaluated in our previous work, Alloy BDW (Al−1Mg−0.1In−0.2Mn) and Alloy 21 (Al−0.2Ga−0.1In−0.1Tl). The inhibitors employed in this study, SnO32−, In(OH)3, BiO33−, Ga(OH)4−, MnO42−, and binary combinations thereof, are either present in Alloys BDW and 21 or have been investigated previously (SnO32−). We found that potassium manganate (K2MnO4) and Na2SnO3+In(OH)3 are effective inhibitor systems, particularly at high discharge rates (400 mA cm−2), but at low discharge rates only manganate offers a significant advantage in coulombic efficiency over the uninhibited solution. Alloy BDW exhibits a very low open circuit (standby) corrosion rate, but its coulombic efficiency under discharge, as determined by delineating the partial anodic and cathodic reactions, was found to be no better than that of aluminium in the same uninhibited solution. Alloy 21 was found to exhibit a comparable performance to Alloy BDW under open circuit conditions and a much higher coulombic efficiency at low discharge rates (100 mA cm−2), but the performance of this alloy under high discharge rate conditions was not determined. Alloy 21 has the significant disadvantage that it contains thallium.