A green electrolyte additive based on Toona Sinensis extract for enhanced performance of alkaline Al-air battery

Abstract

Aqueous aluminum (Al)-air batteries (AABs) have attracted significant attention due to their high theoretical energy density. Nevertheless, the self-corrosion of Al anodes causes a decline in anode utilization and capacity, thereby restricting their commercial feasibility. Herein, Toona Sinensis extract (TSE) is proposed as a green electrolyte additive to reduce the self-corrosion of Al anodes in alkaline AABs. The findings indicate that the utilization of TSE offers a successful strategy for effectively suppressing the self-corrosion of Al anodes, ultimately boosting the discharge performance of AABs. Quercetin, kaempferol, nicotinic acid, phenolic acid, and α-linolenic acid were identified as the main components in TSE through a series of ex-situ/in-situ characterizations. An inhibition efficiency of 51.9 % was achieved by using an optimized electrolyte containing 0.4 g L⁻¹ TSE additive, which helped suppress the pitting corrosion of Al anodes in alkaline electrolyte. Ultimately, the AABs demonstrated a remarkable specific capacity of 2571.4 mAh g^–1 and anode utilization rate of 83.9 %, surpassing the initial capacity of 1278.7 mAh g^–1 and utilization rate of 43.2 %. Density functional theory (DFT) calculations combined with molecular dynamics (MD) simulations reveal that quercetin, kaempferol and nicotinic acid are the most active components in TSE. By forming O-Al and N-Al bonds on the Al anode surface, they can create an adsorption protective film that boosts discharge performance and corrosion inhibition effect in AABs. This work demonstrates that TSE serves as a natural electrolyte additive for AABs, providing a novel approach to improve their performance and commercial feasibility.