In situ oxidation/lithiation reaction of the pure Ni and Ni-Co alloy electrodes were studied in molten Li-0.62/K-0.38 carbonate eutectics saturated with a 0.9O(2) + 0.1CO(2) atmosphere at 923 K. Ni-Co alloy electrodes were prepared on the pure Au foil by the galvanostatic pulse plating method. Open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were employed to investigate the in situ oxidation /lithiation reaction of electrodes. OCP variation of Ni and Ni-Co alloy electrodes was divided into four regions and charge transfer resistance (R-ct) and diffusion resistance (R-diff) measured as a function of OCP/immersion time in EIS experiment strongly depended on the composition of Ni-Co alloy electrodes and the electrochemical-catalytic activity of Ni-Co alloy electrodes was affected by the surface roughness. In XRD analysis and micro-Raman spectroscopy (RS), the lithiation content increased proportionally with the amount of cobalt in Ni-Co alloy electrodes, which was an important factor to determine the electrochemical-catalytic activity of electrodes. (C) 2004 Elsevier Ltd. All fights reserved.