Aqueous zinc–polyaniline secondary battery

An aqueous zinc–polyaniline secondary battery was constituted by the polyaniline synthesized in a mixed solution containing 0.60 mol dm−3 aniline, 1.20 mol dm−3 1-ethyl-3-methylimidazolium-ethyl sulfate (EMIES) and 2.0 mol dm−3 H2SO4, Zn foil and an electrolytic solution containing 2.0 mol dm−3 ZnCl2 and 3.0 mol dm−3 NH4Cl with pH 6.0. The capacity and energy densities of the polyaniline are 141.2 A h kg−1 and 169.4 W h kg−1 for discharge process at 0.5 mA cm−2, respectively, which are much better than those of the polyaniline synthesized in HCl at the same current densities. The battery was successively charged/discharged at constant current densities, the columbic efficiency was 95.5% at 150th cycle, and the energy density of the battery was lower by only 6.0% at 150th cycle than at 1st cycle.