Solid oxide cells (SOCs) are electrochemical devices that convert the chemical energy of a fuel into electricity. With regard to electrodes, the development of materials with mixed conduction properties is a key issue for improving the performance of SOCs at high temperatures. New Cu and Nb co-doping La_1−xSr_xFe_yCo_1−yO_3−δ (LSCF) materials were studied as electrode materials on yttria-stabilized zirconia (YSZ) supports. The results show that Cu_0.05 + Nb_0.05 co-doped LSCF maintains a stable cubic structure even after several heat treatments and has better conductivity than a classically used LSCF.