Organic corrosion inhibitor without discharge retardation of aluminum-air batteries

Aluminum (Al)–air batteries require a high anodic dissolution rate for discharge and low corrosion rates to maximize energy efficiency. However, these requirements are not easy to satisfy because these properties are generally inversely proportional. This study evaluates the effect of adding polyvinyl alcohol (PVA) to a 4.0 M sodium hydroxide electrolyte in 4N grade Al (99.99% purity)–air batteries. The effect of PVA is evaluated by self-corrosion, electrochemical, discharge tests, and surface analysis. In electrochemical tests, PVA lowered the corrosion rate of 4N grade Al and improved the Al–air battery efficiency. The battery performance test yielded a capacity density of 2,264.15 mAh g⁻¹ and an energy density of 3,237.74 Wh kg⁻¹. Also, it was confirmed that PVA acts as a cathodic inhibitor that does not interfere with anode dissolution reaction. PVA is physically adsorbed on the Al surface and inhibits corrosion by its strong attraction to water molecules in an open-circuit state. As the discharging proceeds, the adsorbed PVA is detached from the Al surface without deformation. This process made the Al dissolution reaction not suppressed, thereby improving the battery efficiency.