Performance and long term durability of metal-supported solid oxide fuel cells

A long term durability test is conducted on a large area 10 x 10 cm(2) metal-supported cell. The cell that consists of a porous nickel-iron substrate as a support, an La0.75Sr0.25Cr0.5-Mn0.5O3-delta (LSCM) interlayer, a nano-structured Ce0.55La0.45O2-delta (LDC)-Ni anode, an LDC isolation layer, an La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) electrolyte, a Sm0.15Ce0.85O3-delta (SDC) barrier layer and a SDC-Sm0.5Sr0.5CoO3-delta (SSC) cathode is prepared by using an atmospheric plasma spraying technology. The measured maximum output powers are 40.4, 31.2 and 22.7 W at 750, 700 and 650 degrees C respectively. In the long term durability test, the cell voltages are measured in a constant current mode (400 mA cm(-2)) for 3000 h at 700 degrees C. The measured I-V curves and AC impedance data are used to trace the variations of ohmic and non-ohmic resistances at different times. It is found that the dominant factors in the degradation of the tested cell are the increases of activation polarization and ohmic resistances. The tested cell is heat treated at the condition of 820 degrees C and OCV for 4 h after 500 h durability test, the measured I-V curves and cell voltages show that the tested cell is recovered and demonstrate that the heat treated process at the condition of 820 degrees C and OCV for 4 h is effective to recover the performance of the prepared cell. Based on the measured experimental data and the post microstructure analysis, the degradation of the tested cell is mainly due to the microstructural change in the anode and micro-cracks formed at layer interfaces that have significant thermal expansion mismatches, they cause the increases of activation polarization and ohmic resistances. After the recovery process, it is found the ohmic resistance decreases. (C) 2015 The Ceramic Society of Japan. All rights reserved.