In Situ Measurement of RedOx-Induced Stresses in Electrolyte of Anode-Supported Solid Oxide Fuel Cells Using the Cos<i>α</i> Method

Solid oxide cells (SOCs) are efficient energy-conversion devices; however, they face inadequate durability and mechanical reliability. In this study, in situ stress monitoring was performed using the cos α method to investigate the residual stresses in the yttria-stabilized zirconia (YSZ) electrolyte of a commercial Ni(O)–YSZ supported half cells (Ningbo SOFCMAN and Elcogen AS) during thermal cycling and redox processes, focusing on initial operation and fuel depletion. Reduction in 10% H 2 –N 2 at 700 °C initially caused compressive stress in the YSZ, which then relaxed owing to Ni creep in the Ni–YSZ. Meanwhile, exposure to an oxidizing gas resulted in tensile stresses in the YSZ and subsequent crack formation, highlighting the risk posed by H 2 electrode re-oxidation during high-temperature SOCs operation. During re-oxidation, the stress behavior varied depending on the microstructure, with differences in the Ni–YSZ porosity affecting gas diffusion and likely causing different volume changes in the Ni–YSZ layer. These findings, achieved through in situ monitoring, provide valuable insights for improving the reliability and durability of SOCs.