Ionic liquids (ILs) belong to new branch of salts with unique properties which their applications have been increasing in electrochemical systems especially lithium-ion batteries. In the present work, for the first time, the effects of four ionic liquids as an electrolyte additive in battery's electrolyte were studied on the hydrogen and oxygen evolution overpotential and anodic layer formation on lead-antimony-tin grid alloy of lead acid battery. Cyclic and linear sweep voltammetric methods were used for this study in aqueous sulfuric acid solution. The morphology of grid surface after cyclic redox reaction was studied using scanning electron microscopy. The results show that most of added ionic liquids increase hydrogen overpotential and whereas they have no significant effect on oxygen overpotential. Furthermore ionic liquids increase antimony dissolution that might be related to interaction between Sb3+ and ionic liquids. Crystalline structure of PbSO4 layer changed with presence of ionic liquids and larger PbSO4 crystals were formed with some of them. These additives decrease the porosity of PbSO4 perm selective membrane layer at the surface of electrode. Also cyclic voltammogram on carbon-PbO paste electrode shows that with the presence of ionic liquids, oxidation and reduction peak current intensively increased. (C) 2008 Elsevier B.V. All rights reserved.