Aluminum anode for aluminum–air battery – Part I: Influence of aluminum purity

•The performance of 2N5 Al is not as good as 4N Al due to the impurity layer.•The impurity complex film is diminished with decreasing discharge voltage.•2N5 Al shows similar performance as 4N Al with decreasing discharge voltage.•We find the way to optimize the performance of 2N5 Al as anode on Al–air battery.

2N5 commercial grade aluminum (99.5% purity) leads to the lower aluminum–air battery performances than 4N high pure grade aluminum (99.99% purity) due to impurities itself and formed impurity complex layer which contained Fe, Si, Cu and others. The impurity complex layer of 2N5 grade Al declines the battery voltage on standby status. It also depletes discharge current and battery efficiency at 1.0 V which is general operating voltage of aluminum–air battery. However, the impurity complex layer of 2N5 grade Al is dissolved with decreasing discharge voltage to 0.8 V. This phenomenon leads to improvement of discharge current density and battery efficiency by reducing self-corrosion reaction. This study demonstrates the possibility of use of 2N5 grade Al which is cheaper than 4N grade Al as the anode for aluminum–air battery.