Impact of Li-ions and CO2 on the electrochemical efficiency of Al and Al-4%Sn in KOH electrolyte for alkaline batteries application

Abstract

This study investigates the electrochemical behavior of aluminum (Al) and aluminum‑tin (Al-Sn) alloy as anodes in aluminum-air (Al-air) batteries in a potassium hydroxide (KOH) electrolyte with varying concentrations of lithium hydroxide (LiOH), in both the presence and absence of carbon dioxide gas (CO2). Experimental techniques such as potentiodynamic polarization (Tafel behavior), galvanostatic charging-discharging processes, and electrochemical impedance spectroscopy (EIS) were employed. Characterization techniques including X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) were utilized to analyze the surface products of each electrode. The findings indicate a significant decrease in the corrosion current density (icorr.) for both two electrodes with increasing LiOH concentration, however, Al-Sn exhibits lower values than those of commercial Al. Moreover, the presence of Li-ions revealed an interesting phenomenon of Al, where icorr. gradually decreased with temperature rise. Also, in the presence of CO2, icorr. significantly decreased for both two electrodes, particularly Al-Sn, indicating complete repression of the corrosion process on the surface. The corrosion rate of the studied electrodes in basic solutions, with and without CO2, follows the order: KOH > KOH + LiOH > KOH + LiOH + CO2. Galvanostatic charge-discharge measurements demonstrated higher capacity, improved electrochemical performance, and excellent charge-discharge behavior in the presence of LiOH. The electrochemical findings align well with the results from XRD, SEM, and EDX analysis.