Effect of phosphate and vanadate as electrolyte additives on the performance of Mg-air batteries

In this study, phosphate and vanadate were used as additives in the NaCl electrolyte in Mg-air batteries. The inhibiting effect of these additives on the corrosion of the AZ31 Mg alloy was investigated through electrochemical tests and the battery performance was evaluated through constant-current discharging tests. The phosphate had a more pronounced inhibiting effect than the vanadate. The corrosion current densities of AZ31 in the blank, phosphate-containing, and vanadate-containing electrolytes were 79.43, 1.98, and 22.38 μA cm−2, respectively. However, both the presence of the phosphate and vanadate significantly improved the battery performance, especially under intermittent discharging. Under constant-current continuous discharging, the anodic efficiencies of the Mg-air batteries with the blank, phosphate-containing, and vanadate-containing electrolytes were 65.5%, 73.1%, and 69.9%, respectively, while those under constant-current intermittent discharging were 59.7%, 72.5%, and 68.8%, respectively. Moreover, the addition of the phosphate and the vanadate resulted in the formation of a loosely packed film of the discharging products on the Mg anode, which also helped improve the battery performance. [Display omitted] •Effect of phosphate and vanadate on the performance of Mg-air batteries is studied.•The phosphate had a better inhibiting effect on Mg alloys than the vanadate.•The phosphate and vanadate improved the anodic efficiencies of the batteries.•The phosphate and vanadate improved the structure of the discharge products.