This study is introducing the application of some acidic ionic liquids (ILs), as an electrolyte additive in lead-acid batteries. A family of alkylammonium hydrogen sulfate ionic liquids, which are different in the number of alkyl chain, is investigated with the aim to compare their effects on the electrochemical behavior of Pb–Sb–Sn alloy in sulfuric acid solution. The hydrogen and oxygen gas evolution potential and anodic layer characteristics were investigated employing cyclic and linear sweep voltammetric methods. The morphological changes of the O 4 layer that formed on the electrode surface were confirmed using scanning electron microscopy (SEM). Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and an equivalent circuit analysis were used to evaluate the corrosion behaviors of the Pb–Sb–Sn alloy in the presence of ILs. Also, the electrochemical effects of ILs in conversion of O 4 to PbO 2 and vice versa were investigated by carbon-PbO paste electrode.The obtained results indicate that in the presence of all studied ionic liquids, fewer and smaller O 4 crystals are formed on the electrode surface. All studied ILs increase hydrogen and oxygen evolution overpotential and antimony dissolution. However, they have different effects on the grid corrosion rate. Cyclic voltammogram of carbon-PbO electrode shows that in the presence of ionic liquids, oxidation and reduction peak currents increase, while reversibility decreases. Also, investigating of a family of alkylammonium hydrogen sulfate ionic liquids shows that electrochemical behaviors of lead alloy are mainly under the influence of number of alkyl chain in alkylammonium cations. Hydrogen evolution potential has a linear correlation with the number of alkyl chain. However, oxygen evolution overpotential depends on the influence amount of IL on morphological characterizations of the lead sulfate layer. It seems that butylammonium hydrogen sulfates reveal a beneficial effect on the electrochemical behavior of lead-acid battery specially, if they have high number alkyl chain in their cations.
