In-situ protective interphase constructed by ZnC₂O₄ for boosted longevity of alkaline Al-air batteries

Al-air batteries hold promising prospects in mobile/static energy storage thanks to the ultra-high specific capacity, abundant resources, and environmental friendliness. However, hydrogen evolution reaction (HER) of Al anode leads to an irreversible loss of active metal, and a significant reduction in battery energy efficiency. In this work, an in-situ dense protective interphase is innovatively constructed on the Al anode through a synergistic “displacement-complexation” mechanism. After modifying the 6 M KOH electrolyte with 0.23 M ZnC₂O₄, HER inhibition and Zn deposition are regulated optimally. Consequently, the battery delivers a specific capacity of 2028.43 mAh/g and an anode efficiency of 68.07 % at 20 mA/cm², while achieving an absolute HER inhibition efficiency of 62.83 %. It is found that the highly electronegative carbonyl oxygen in C₂O₄^2- ions preferentially occupies HER active sites via electrostatic adsorption, and promotes coordinate complexation with interfacial metal ions due to the low energy band gap of 3.50 eV, forming a stable protective interphase. This study provides a unique strategy for boosting the longevity of alkaline Al-air batteries.