Fuel Cells, Volume 13, Issue 5, pages 712–719, 2013.
H.-T. Lim, S. C. Hwang, M. G. Jung,H. W. Park, M. Y. Park, S.-S. Lee, Y.-G. Jung.
School of Nano and Advanced Materials Engineering, Changwon National University, Changwon, Gyeongnam 641-773, Republic of Korea and
Fuel Cell Project, Research Institute of Industrial Science and Technology (RIST), Pohang, Gyeongbuk 790-600, Republic of Korea.
The degradation mechanism of anode-supported planar solid oxide fuel cells is investigated in the present work. We fabricate a large-area (10 cm × 10 cm) cell and carry out a long-term test with the assembly components. A constant current of ∼0.4 A cm–2 is applied to the cell for ∼3,100 h, and the furnace temperature is controlled in the sequence 750–800–750 °C to investigate the effect of operating temperature and thermal cycling on the degradation rate. Impedance spectra and current–voltage characteristics are measured during the operation in order to trace any increase in Ohmic and non-Ohmic resistance as a function of time. The degradation rate is rapid during the operation at the higher temperature of ∼800 °C compared to that during the operation at ∼750 °C. Even after cooling down to ∼750 °C, that rate is still accelerated. The main contribution to the cell degradation is from an increase in the Ohmic resistance. Postmaterial analyses indicate that the cathode is delaminated at the electrolyte/cathode interface, which is attributed to the difference in thermal expansion coefficient (TEC). Thus, the present results emphasize the importance of matching the TEC between cell layers, especially under severe operating conditions such as long duration and complex thermal cycling.
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