Zinc carboxylate optimization strategy for extending Al-air battery system's lifetime

Abstract

Although Al-air batteries are expected to be the candidates for energy conversion systems in renewable energy market due to the higher energy density, richer reserves, and lighter mass of Al metal, the anode self-discharge is seen as a notorious issue that seriously sacrifices battery durability and stability. Herein, we propose zinc carboxylate inhibition of anode self-discharge for enhancing Al-air battery's lifetime, where the ionized Zn²⁺ induces a Zn guard on Al surface, and the hydrolysate RCOOH dominates an adsorption layer on the outer surface of Zn, ensuring a double protection for metal anode by means of advanced “one stone two birds” strategy. The results show that the typical zinc carboxylates improve the absolute anticorrosion efficiency of anode greatly, especially the maximum of 92.24% after zinc malate optimization. Furthermore, battery capacity and anode efficiency are as high as 2685.20 mAh g⁻¹ and 90.11% at 20 mA cm⁻² respectively. The cyclic discharge lifetime of system (0.12 g fuel) exceeds 19.01 h, which is 1.72 times longer than traditional optimization. Finally, the optimization mechanism is revealed based on Monte Carlo simulation and density functional theory calculation, which the double CO groups in the hydrolysate of zinc malate dominates the harmonious interaction between RCOOH adsorption layer and active metals, exhibiting a high-energy efficiency and long-lifetime Al-air battery power system.