Thermally Driven SOFC Degradation in 4D: Part II. Macroscale

Abstract

© The Author(s) 2018. Published by ECS. An inability to withstand rapid thermal cycling remains a major challenge for solid oxide fuel cells (SOFCs). Delamination of the anode and electrolyte layers due to mismatch in the thermal expansion coefficients (TEC) is a significant source of degradation. The first part of these studies inspected the interactions at the microscale, while this work presents the second of the two-part study and investigates such degradation with a focus on the macroscale. During thermal cycling the cell walls contracted and the interface concaved. A critical transition is thought to be triggered by an upper limit on the thermal ramp-rate, which in this case relates to rates above 20°C·min−1. Additionally, the interfacial contact was observed to reduce with each thermal cycle progressing linearly until the aforementioned critical point was reached, after which a significant reduction in the degradation rate was observed. Interfacial curvature may also be responsible for cracking within the anode layer due to the localized tensile strain experienced during the bending process. This two-part study presents the first extended 4D investigation into the effects of thermal cycling at sub-micron resolution using only lab-based instruments. These results present valuable insight into interfacial delamination and anode cracking important in both cell design and operation.