Life testing of LSM-YSZ composite electrodes under reversing-current operation

• Published in: Physical chemistry chemical physics : PCCP 2013-10, Vol.15 (4), p.17257-17262
• Main Authors: Hughes, Gareth A, Yakal-Kremski, Kyle, Barnett, Scott A
• Format: Article
• Language: English
• Subjects: Chemistry; Current density; Degradation; Delaminating; Delamination; Electrochemistry; Electrodes; Electrolytic cells; Exact sciences and technology; General and physical chemistry; Oxides; Scanning electron microscopy; Surface physical chemistry
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp52973h

Durability testing of solid oxide cell electrodes in reversing-current and constant-current operation modes is presented. (La 0.8 Sr 0.2 ) 0.98 MnO 3− δ -Zr 0.84 Y 0.16 O 2− γ (LSM-YSZ) symmetric cells were tested at 800 °C in air with current densities of 0.5 and 1.5 A cm −2 , with current cycle periods of 1 and 12 h. A continuous increase in both ohmic and polarization resistance was observed, via Electrochemical Impedance Spectroscopy (EIS), for cells tested with a reversing current of 1.5 A cm −2 , whereas cells tested at 0.5 A cm −2 showed no measurable resistance increase. The resistance degradation was explained by delamination in the electrode, observed by post-test Scanning Electron Microscopy (SEM), near the interface with the electrolyte for the 1.5 A cm −2 cells, but not for those tested at 0.5 A cm −2 . Current cycle period also impacted the degradation observed at 1.5 A cm −2 : both the rate of resistance increase and the extent of post-test delamination decreased on going from constant current mode to a 12 h period to a 1 h period. The results indicate that lower current densities and reversing-current operation are desirable to maximize the lifetime of solid oxide cells. Lifetime of current cycled solid oxide cells improved with shorter cycling period and lower current density.