Inhibiting anodic parasitic reaction for high-performance Al-air batteries via a multi-functional hybrid additive

Al-air batteries have promising prospects due to their high theoretical specific capacity and energy density. However, the severe parasitic hydrogen evolution reaction (HER) on the Al surface in aqueous electrolytes is still the main challenge. Herein, we developed a green, low-cost, and multi-functional ZnO/glucose hybrid additive (ZGHA) to continuously inhibit the parasitic HER and stabilize the Al-metal anode. The inhibition mechanism was revealed via various characterizations and theoretical calculations. The glucose could simultaneously decrease water activity and form an adsorption layer. Besides, the addition of inorganic ZnO helps to form a Zn-containing layer. Impressively, ZnO and glucose show a synergy. The glucose molecule can adsorb on the Zn-containing layer to achieve a more uniform and firmer Zn-containing protective layer on the Al surface. A significant suppression on the parasitic HER and self-corrosion on the Al-metal anode is thereby achieved. The specific capacity and energy density of the Al-air battery are remarkably promoted to 2271.1 mAh gAl−1 and 2446.9 Wh kgAl−1. This work is instructive for developing better electrolyte additives for long-life and green Al-air batteries and could provide a reference for the exploration of anode/electrolyte interface.