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

Electrochemical impedance spectroscopy (EIS) has been widely used in the performance evaluation and degradation diagnosis of SOFC. However, it was found that the EIS results measured at OCV did not necessarily reflect the output performance at high current density. A button cell with an active area of 0.45 cm2 and an industrial-size cell with an active area of 100 cm2 with similar components of porous Ni-YSZ|YSZ|GDC|GDC-LSCF porous were prepared and tested to investigate the correlation between the evolution of performance and EIS at OCV. It was found that the activation process and the humidity degree of fuel gas had a significant impact, i.e. the EIS measured at OCV did not directly correlate with the output performance at high current density. However, the EIS measured at OCV could reflect the output performance after activation process.