Polyaniline (PANI) films doped with Ni2+ (PANI/Ni2+) were synthesized by cyclic voltammetry (CV) on stainless steel (SS) substrates in 0.2 mol/L aniline (An) and 0.5 mol/L sulfuric acid (H2SO4) electrolyte with various concentration of nickel sulfate (NiSO4). The structure and morphology of PANI/Ni2+ films were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical properties of PANI/Ni2+ films were investigated by cyclic voltammetry, galvanostatic charge-discharge test and electrochemical impedance spectroscopy (EIS) in 0.5 mol/L H2SO4 electrolyte in three-electrode system. The results suggest that the growth rate of PANI was greatly increased, which may arise from the interactions between PANI chain and Ni2+. The PANI/Ni2+ films show a larger specific capacitance of 658.3 F/g at a current density of 5 mA/cm(2) and lower resistance compared with the pure PANI film. The results indicate that the PANI/Ni2+ films are promising material for supercapacitors. (C) 2012 Elsevier Ltd. All rights reserved.