Influence of (La, Sr) MnO sub(3+ delta ) cathode composition on cathode/electrolyte interfacial structure during long-term operation of solid oxide fuel cells

• Published in: Journal of power sources Vol. 242; pp. 790 - 796
• Main Authors: Matsui, T, Mikami, Y, Muroyama, H, Eguchi, K
• Format: Journal Article
• Language: English
• Published: 15.11.2013
• ISSN: 0378-7753

Time-dependent events during operation of SOFCs, i.e., performance enhancement and/or deterioration, can be readily observed for the cell composed of strontium-doped lanthanum manganite (LSM) cathode and yttria-stabilized zirconia (YSZ) electrolyte, concomitant with the change in interfacial structure of LSM/YSZ. The influence of LSM composition on the electrochemical properties and microstructure of LSM/YSZ interface during prolonged operation was investigated. Four different LSM cathodes were used and the change in microstructure, especially TPB-length, was evaluated quantitatively by a focused ion beam-scanning electron microscope (FIB-SEM). For LSM cathodes with A-site deficient compositions, the change in TPB-length had a minor contribution to the performance enhancement after 20 h of galvanostatic operation. On the other hand, for 100 h duration an increase in cathode overpotential was confirmed, accompanied with the formation of thin layer of LSM over YSZ electrolyte. A series of phenomena were triggered by the change in oxygen nonstoichiometry of LSM under polarized states. The mechanism for microstructural change was proposed and the long-term stability of LSM/YSZ interface was discussed.