High power density solid oxide electrochemical cells were developed using nanostructure-controlled composite powder consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) for electrode material. The SSC-SDC nano-composite powder, which was synthesized by spray pyrolysis, had a narrow particle size distribution (D-10, D-50, and D-90 of 0.59, 0.71, and 0.94 mu m, respectively), and individual particles were spherical, composing of nano-size SSC and SDC fragments (approximately 10-15 nm). The application of the powder to a cathode for an anode-supported solid oxide fuel cell (SOFC) realized extremely fine cathode microstructure and excellent cell performance. The anode-supported SOFC with the SSC-SDC cathode achieved maximum power density of 3.65, 2.44, 1.43, and 0.76W cm(-2) at 800, 750, 700, and 650 degrees C, respectively, using humidified H-2 as fuel and air as oxidant This result could be explained by the extended electrochemically active region in the cathode induced by controlling the structure of the starting powder at the nano-order level. (C) 2015 Elsevier B.V. All rights reserved.