Yttria-stabilized zirconia (8 mol%; YSZ) or samaria-doped ceria (Sm0.2Ce0.8O2; SDC)-modified La0.65Sr0.15MnO3 (LSM) composite cathodes were fabricated by formation of an YSZ or SDC film at the triple-phase boundary (TPB) of LSNI/YSZ/gas. The YSZ film greatly enlarged the number of electrochemical reaction sites (ERSs) by increasing the TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 mum thickness) supported on an anode and then I-V characterization and ac impedance analyses were performed at temperatures between 700 and 800 degreesC. As a result of the impedance analysis on the cell at 800 degreesC, with humidified hydrogen as the fuel and air as the oxidant, the element R-2 around the frequency of 1000 Hz is identified as the anode polarization, R-2 around the frequency of 100 Hz is identified as the cathode polarization and R-3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The maximum power densities of the cell modified by the SDC sol-gel coating were about 0.53 W/cm(2) at 750 degreesC and about 0.19 W/cm(2) at 650 degreesC. The result implied that deposition of SDC in the pore surface of the cathode increased the area of the TPB, resulting in a decrease of cathode polarization and improved cell performance.