Anti‐corrosive additives for alkaline electrolyte in Al‐air batteries: NH4VO3 and polyoxometalates

Aluminum‐air batteries are a promising alternative for portable energy storage. However, one of the significant issues in this technology is the corrosion of aluminum in alkaline electrolytes. In this study, we explored heteropolyacids (HPAs) H5PMo11Al0.5V0.5O40 and H6PMo11AlO40 as possible anti‐corrosive additives in Al7475, Al6062, and Al5052 commercial alloys. We also investigated the anti‐corrosive properties of commercial NH4VO3 and ZnO. Concerning HPAs, only H6PMo11AlO40 in combination with Al5052 showed anti‐corrosive activity. However, ZnO did not present anti‐corrosive properties in Al6062 alloy, while NH4VO3 presented anti‐corrosive properties for all three alloys. The combination of carboxymethylcellulose with NH4VO3 further improved the anti‐corrosive properties in the Al7475 alloy. We observed by using 2D Raman imaging the formation of polymeric forms of tetrahedral V+5O4 over the surface of three alloys. The main conclusion of our studies is that NH4VO3 combined with carboxymethylcellulose is a promising anti‐corrosive in the alkaline electrolyte of aluminum‐air batteries. NH4VO3 in alkaline electrolytes form a protective polymeric layer of tetrahedric V+5O4 species over Al5052, Al6062, and Al7475 alloys that inhibits corrosion. Combination with carboxymethyl cellulose forms a more stable layer that makes it promising for application in aluminum‐air batteries.