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Symmetrical solid oxide fuel cells (SSOFCs) with identical anode and cathode have many benefits compared with traditional SOFCs. However, it is still a challenge to find high performance electrode materials with excellent catalytic activity and preferable stability under both reducing and oxidizing atmosphere. Here, a novel Ba 0.9 La 0.1 Co 0.7 Fe 0.2 Nb 0.1 O 3-δ (BLCFN) perovskite electrode has been developed as promising symmetrical electrode material for SSOFCs. The A-site non-stoichiometry introduced in BLCFN simultaneously enhances both the cathode and anode electrocatalytic performance. The cathode polarization resistance of BLCFN with 5% deficiency is decreased by 28.6% to 0.05 Ω·cm2 at 750°C in air, which can be mainly attributed to the increase of oxygen vacancy concentration via partial ionic defect. The BLCFN anode polarization resistance is reduced by 42.1% to 0.11 Ω·cm2 at 750°C in 5% H 2 /N 2. The promoted hydrogen oxidation reaction activity of BLCFN is related to the exsolved homogeneous Co-Fe nanoparticles from BL95CFN substrate in reducing atmosphere. The full cell with BL95CFN symmetrical electrodes displays high redox stability through reversing the flow of wet hydrogen and ambient air. Additionally, this SSOFCs with strong anchor characteristic of exsolved Co-Fe nanoparticles shows excellent coking-tolerance using methane fuel compared with traditional Ni-SDC anode. This work provides a potential way towards the development of high-performance, excellent redox-stable and coking-tolerant SSOFCs. [ABSTRACT FROM AUTHOR]