Benchmarking of Aluminum Alloys Processed by High-Pressure Torsion: Al-3% Mg Alloy for High-Energy Density Al-Air Batteries

Aluminum-air batteries are an up-and-coming alternative for high-energy density storage. However, one of the main drawbacks is the self-corrosion of aluminum alloys in alkaline electrolytes, where the batteries perform best. For that reason, new aluminum alloys resistant to corrosion are required. Severe plastic deformation (SPD) techniques are versatile methodologies that result in metals with an ultrafine microstructure and can be used to prepare new alloys or modify their microstructure. In this study, 4N-Al (99,99%) and Al-2% Fe, Al-3% Mg, Al 1050, Al 5052, and Al 6063 alloys were studied as-received and after SPD by high-pressure torsion (HPT). We observed that the ultrafine-grained microstructure improved the resistance toward corrosion. However, the main determining factor in the resistance toward corrosion is the cathodic shift in the corrosion potential, as observed by mass loss and potentiodynamic polarization plots. Based on that, Al-3%Mg was chosen to be tested in an in-house designed aluminum-air cell with an alkaline gel electrolyte. The battery delivered up to 1407 mA h g-1, 1.7 V, and an operation time of 70 h at a current of 2 mA cm-2. Therefore, HPT represents an opportunity to easily prepare and benchmark new aluminum alloys for metal-air battery applications.