A-site deficient (La0.6Sr0.4)1–x Co0.2Fe0.6Nb0.2O3–δ (x = 0, 0.05 and 0.10) symmetrical electrodes (hereafter denoted as LSCFN, LSCFN5, and LSCFN10, respectively) are obtained by doping Nb at the B site of La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) cathode. All three electrodes display excellent structural stability both in cathode and anode conditions. The thermal expansion coefficients of the electrodes range within 13.4–14.3 × 10−6 K−1 at 30–900 °C in air and 5% H2/Ar, and these values are close to those of common electrolytes. Furthermore, 20-h electrochemical impedance stability test results indicate that LSCFN10 as anode or cathode possesses excellent electrochemical stability. The introduction of A-site deficiency into LSCFN results in obviously increased oxygen–vacancy concentration and improved electrochemical performance. A single cell with LSCFN10 symmetrical electrode operates well in various fuels, such as H2, sulfur-containing syngas, ethanol, and CH4, and shows favorable electrochemical stability running on CH4 fuel.