Strain Accumulation Study of Ni-based Anode-Supported Solid Oxide Fuel Cells under Partial-Redox Cycling Conditions

摘要

Partial-redox cycles lead to severe degradation (electrolyte cracks) to Ni-based anode-supported solidoxide fuel cell (SOFC) when the cycle number is high (~10), even though the oxidation degree isbelow the critical level (~50%). Time controlled partial-redox cycles were implemented in SOFCs toinvestigate the effect of strain accumulation. It is found that this artial-redoxcycle in which anodewas oxidized partially (10%-40%) and then fully reduced, may bring irreversible cell expansion andmechanical damage, although it showed hardly any crack in the first few cycles. This phenomenonrequires a more rigid re-oxidation level of restriction for those NASCs designed living through dozensor even hundreds of redox cycles. Strain accumulation effect was observed when the anode re- oxidation degree reached ca.20%, below which the cell was "safe". Both NiO and porosity gradientalong anode thickness arise. SEM studies reveal that the redox front moves towards the electrolyte asredox cycle number increases, although the re-oxidation degree is constant. And the chemical reactionsare considered the driving force for redox front move, which constantly bring irreversible strain to theanode.