A self-regulated shielding layer induced by an electrolyte additive for alkaline Al-air batteries

Aqueous Al-air batteries (AABs) are considered promising electrochemical energy devices due to their high-energy density, high-capacity density, and stable discharge voltage. However, the self-corrosion, passivation, and parasitic hydrogen precipitation side reactions in the aqueous electrolyte degrade the performance of these batteries, limiting their development. To overcome the problems related to the use of AABs, we introduce ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) as an additive to the alkaline electrolyte. EDTA-2Na adsorbs strongly to the Al anode interface creating a protective layer capable of inhibiting water-induced parasitic reactions. In fact, in the presence of the additive, the hydrogen evolution tests have shown that the hydrogen evolution rate decreased from 0.70 to 0.30 mL cm^-2 min^-1. In addition, the electrochemical tests indicated an inhibition efficiency of 55%, the full-cell discharge tests suggested an increase in the specific capacity density of the battery from 943.6 to 2381.7 mA h g^-1 and the anode utilization increased from 31.6% to 80.9%, greatly improving the performance of the battery. Surface characterization of the Al alloy surface was also carried out to investigate the adsorption of EDTA-2Na on it. This electrolyte modification strategy provides a promising option for modulating the anode/electrolyte interface chemistry to achieve high-performance AAB.