High conductive (LiNaK)2CO3Ce0.85Sm0.15O2 electrolyte compositions for IT-SOFC applications

Composite electrolytes of lithium, sodium, and potassium carbonate ((LiNaK)2CO3), and samarium doped ceria (SDC) have been synthesized and the carbonate content optimized to study conductivity and its performance in intermediate-temperature solid oxide fuel cell (IT-SOFC). Electrolyte compositions of 20, 25, 30, 35, 45 wt% (LiNaK)2CO3-SDC are fabricated and the physical and electrochemical characterization is carried out using X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscope, and current-voltage measurements. The ionic conductivity of (LiNaK)2CO3-SDC electrolytes increases with increasing carbonate content. The best ionic conductivity is obtained for 45 wt% (LiNaK)2CO3-SDC composite electrolyte (0.72 S cm−1 at 600 °C) followed by the 35 wt% (LiNaK)2CO3-SDC composite electrolyte (0.55 S cm−1 at 600 °C). The symmetrical cell of the 35 wt% (LiNaK)2CO3-SDC composite electrolyte with lanthanum strontium cobalt ferrite (LSCF) electrode in air gives an area specific resistance of 0.155 Ω cm2 at 500 °C. The maximum power density of the fuel cell using 35 wt% (LiNaK)2CO3-SDC composite electrolyte, composite NiO anode and composite LSCF cathode is found to be 801 mW cm−2 at 550 °C.