Degradation patterns and mechanisms of solid oxide fuel cells under rapid thermal cycling at various current densities

Solid oxide fuel cells (SOFCs) are promising alternative energy systems to address global climate change and the energy crisis. NiO-yttria stabilized zirconia (YSZ) anode-supported SOFCs are approaching commercialization, yet the influence of operating conditions on long-term thermal stability remains insufficiently explored. This study evaluates durability under current densities of 0.5, 1.0, and 1.5 A cm⁻² with repeated temperature cycling between 400 °C and 700 °C (10 °C·min⁻¹). After 75 cycles, operating voltages decrease from 0.99 V to 0.91 V (0.5 A cm⁻²), 0.90 V–0.77 V (1.0 A cm⁻²), and 0.88 V–0.69 V (1.5 A cm⁻²), corresponding to degradation rates of 1.0, 1.7, and 2.5 mV·cycle⁻¹, respectively. Cells operated under higher current densities experience greater performance degradation and higher area-specific resistances than those operated at lower current densities. Post-mortem analysis further reveals severe microstructural damage at high currents, causing an YSZ electrolyte to crumble into a powder-like form. Additionally, significant Ni depletion on the anode side and the formation of Sr-enriched regions are observed—both contributing to accelerated degradation at higher current densities. This study contributes to our understanding of the degradation phenomenon of SOFCs during thermal cycles and underlying degradation mechanisms, ultimately aiding in the design of more robust cells.