The Correlation of EIS and Performance of Button-Size and Industrial-Size Planar SOFCs Under Different Operating Conditions

Abstract

Reversible solid oxide cell (RSOC) is a new technology for energy storage with the advantages of high efficiency and high energy density, combining solid oxide fuel cell (SOFC) mode and solid oxide electrolysis cell (SOEC) mode to achieve two functions in one device. The commercialization of RSOC is limited by the severe degradation of air electrodes during the operation of SOEC. Anode supported cells with yttria-stabilized zirconia (YSZ) electrolytes, Ni/YSZ hydrogen electrodes and perovskite oxygen electrodes with lanthanum strontium cobalt ferrite (LSCF) were tested and the reversible operation has been demonstrated. The electrochemical performance and stability in reversible mode of the cells are demonstrated under 650℃，700℃，750℃ with different composition of fuel gas (30% H2O/70%H2, 50% H2O/50%H2 and 70%H2O/30%H2) and current density (0.5A/cm2 and 1.0 A/cm2) through the experiment research. Post-test is also used to assist in analyzing the degradation mechanism. It is found that the degradation is more severe under SOEC mode at high current density (1.0 A/cm2) and the alternative operation of two modes helps to mitigate the degradation of cells comparing with operating in SOEC mode. Operation under SOFC mode plays a restorative role through reducing the high oxygen partial pressure at the oxygen electrode caused by SOEC mode operation, thus mitigating the degradation of the cell. This study signifies the difference between the SOEC and SOFC mode and provides insight in the operating mechanism of RSOC.