In this work the performance of NiO and a novel cathode material preoxidized nickel-niobium alloy were investigated. It is found that under a cathode atmosphere of p(CO2)/p(O-2) = 0.67 atm/0.33 atm, the equilibrium solubility of nickel ions in (Li-0.62, K-0.38)(2)CO3 melt at 650 degreesC is about 17 ppm for the nickel oxide electrode and 8 ppm for the preoxidized nickel-niobium alloy electrode. The improvement in the stability of material in the melt may be attributed to the formation of a more dense nodular structure for the nickel-niobium alloy electrode when compared with a Ni electrode during preoxidation. The formation of a dense nodular structure for the nickel-niobium alloy electrode depresses the dissolution of NiO from the electrode into the carbonate melt and, accordingly, enhances the stability of the electrode material in the melt. The polarization performance of the NiO cathode was improved by electrodeposition of niobium. As far as the thermal stability and the polarization performance are concerned, the preoxidized nickel-niobium alloy can be considered as a candidate for the cathode material of MCFCs.