Effect of indium content on the discharge properties of Al-Mg-Ga based anodes in neutral Al-air batteries

The effects of varying In concentrations on the electrochemical and discharge performance of Al-0.5 Mg-xIn-0.05Ga (x = 0.4, 0.2, 0.1, 0.05 wt%) alloy anodes in a 2M NaCl neutral electrolyte have been systematically investigated in this study. It is found that an appropriate In content (0.1–0.2 wt%) enhances discharge performance by reducing localized corrosion associated with Ga and promoting intragranular segregation, which facilitates uniform anodic dissolution and improves overall anodic utilization. In contrast, excessive In (≥0.4 wt%) leads to significant segregation of In at the grain boundaries, resulting in severe intergranular corrosion of the alloy. Moreover, it also significantly hinders charge transfer, with the discharge products of In forming a layer on the electrode surface, thereby obstructing the dissolution of Al, both contributing to a decline in discharge performance. Furthermore, the increase in In concentration shifts the dominant diffusion mechanism from Al³⁺ to In³⁺, considerably affecting the mass transfer between the electrode surface and the electrolyte. Alloy 3 (Al-0.5Mg-0.1In-0.05Ga) demonstrating the best performance at a current density of 5 mA cm⁻², achieving an energy density of 3454.44 Wh kg⁻¹, a working voltage of 1.291V, and an anodic utilization rate of 93.22 %. This work provides valuable insights for the development of high-performance neutral Al-air batteries.