Phase-Field Modelling of Microstructure Evolution in Solid Oxide Cells

Abstract

Solid Oxide Cell (SOC) is one of the most promising energy conversion devices due to its high efficiency, flexible fuel adaptability, and low pollutant emission. By changing the operation condition, the SOC can be operated as a solid oxide fuel cell (SOFC) to convert chemical energy to electricity or as a solid oxide electrolysis cell (SOEC) to store electricity in the way of chemical energy. However, the performance degradation of SOCs caused by microstructure evolution and phase transition during long-term operation, and the stress-induced structure damage limit the SOC’s lifetime. This is one of the most challenging problems to be tackled on the way to commercialize the SOC technology. To clarify degradation mechanisms and develop counter-acting measures, long-term testing combined with detailed post-mortem characterization is one common approach, but this is often associated with extensive amount of experimental work and long research time and thus very costly. Instead, many researchers have devoted their efforts to investigating the degradation phenomena using computational modelling or simulations. Phase field model, which has been widely employed to study microstructure evolution of alloy materials during solidification, aging etc., has also been utilized in the SOC research, to illustrate the microstructure evolution during long-term operation from micron to millimeter scale, with the possibility of taking into account the mechanical properties as well. In this article, the principle of the phase field method and different models are introduced first, following with detailed examples published in literature on phase field modeling of various (degradation) phenomena in SOCs. Finally, possible strategies coupling modelling and experimental research in optimizing SOC performance and microstructure is discussed.