Friction stir processing induced elctrochemical performance improvement of commercial Al for Al-air battery

Friction stir processing (FSP) is applied in the treatment of low cost commercial purity Al (CP-Al) containing iron impurity element with the aim of optimizing the electrochemical properties and discharge performance of CP-Al as the anode of Al-air battery. FSP induced severe plastic deformation effects not only significantly refines CP-Al grains which have an average size of 3 μm but also leads to the fragmentation and the reduction in the amount of Al-Fe phase. Due to the above reasons induced by FSP, the corrosion resistance of CP-Al is increased, which is proved by hydrogen evolution rate test, potentiodynamic polarization measurement and EIS test; on the other hand, more negative corrosion potential values of CP-Al are obtained, indicating both the electrochemical activity and corrosion resistance of CP-Al are enhanced simultaneously. FSP make the discharge performance of CP-Al anode more stable and the average values of discharge potential, energy density as well as utilization of CP-Al anode are significantly increase from 1.054V/1251 mWh g⁻¹/39.8% to 1.116V/1674 mWh g⁻¹/50.3% at 20 mA∙cm⁻². Meanwhile, the power densities of two batteries with C-Al and FSP-Al anodes are 44.38 and 47.17 mW cm⁻² at 50 mA cm⁻², and the difference of which reached a maximum of 2.79 mW cm⁻². The improvements in electrical properties and discharge performance of CP-Al anode can be attributed to the microstructural refinement and the decrease in self-corrosion of CP-Al induced by FSP.