Towards Comprehensive Description of Stack Durability/Reliability Behavior

A new five‐year NEDO project on durability, on the basis of past two projects on SOFC durability/reliability, places an emphasis on simulation technologies to be utilized in comparison with measured long term stack behaviors and in prediction for 90,000 h durability. To extract true degradation issues, use is made of stack materials tested for a long term operation or for thermal cycles; to further confirm the mechanisms, use is made of single cells or button cells for specified issues. This makes it possible to correlate degradation behaviors of cell components with operational conditions such as temperature and oxygen potential with an aid of predetermination of microstructures of electrodes by FIB‐SEM or of the impurity levels inside major components at the beginning of cell operation. There are two major streams in such a comprehensive treatment of degradation; one is to predict the stack performance, the other being the prediction of mechanical instability. These will be described in details with special emphases on impurity effects and anomalous diffusion properties associated with respective extracted degradation issues.