Enhanced discharge performance of AM60-0.6La anode for Mg-air battery via grain structure modification and secondary phase control

Abstract

The study investigates the effect of hot-rolling on enhancing the performance of a magnesium alloy anode in a magnesium-air battery. The hot-rolling process may influence the anode corrosion and discharge behavior by altering the alloy's microstructure. Specifically, we investigated whether the hot-rolling parameters (rolling reduction) could enhance the discharge performance of the Mg-6Al-0.3Mn-0.6La (AM60-0.6La) alloy anode. The results indicated that the rolling process facilitated the formation of a more effective passive film on the surface of the AM60-0.6La alloy under polarized conditions, thereby partially offsetting the corrosion-promoting effect induced by grain refinement. The rolling reductions applied to the AM60-0.6La alloy were 20 %, 40 %, and 60 %, respectively. It was found that the rolling process not only fragmented certain coarse grains, triggering dynamic recrystallization and dynamic recovery, but also disrupted the structure of the second phase, causing it to fracture and effectively increasing the active surface area for discharge in the magnesium alloy. Moreover, the reduced accumulation of discharge products and the presence of a more uniform corrosion morphology confirmed the improved discharge performance. A moderate rolling reduction (20 %) resulted in the most significant enhancement in the properties of the AM60-0.6La alloy. For instance, at a current density of 10 mA‧cm⁻², the alloy exhibited a discharge voltage of 1.323 V and an anode efficiency of 65.2 %.