Advanced microstructure characterization and microstructural evolution of porous cermet electrodes in solid oxide cells: a comprehensive review

Solid oxide cells (SOCs), capable of interconverting electrical and chemical energy, have emerged as one of the key technologies for the future multi-energy complementary grid. However, the commercialization of SOCs is hindered by poor long-term stability, attributed in large-part to the microstructural evolution of the electrodes, which results in the loss of active reaction sites, blockage of gas transport pathways, and degradation of mechanical properties. Owing to recently developed three-dimensional (3D) microstructure reconstruction techniques, the microstructural evolution of SOC electrodes can now be investigated quantitatively. This review highlights insights gained from studies of the microstructural evolution of porous cermet SOC electrodes during long-term operation and redox cycling, and the corresponding effects on electrochemical and mechanical performance, with particular attention to investigations using 3D reconstruction technologies. The influencing parameters and the possible strategies to mitigate microstructure evolution-induced degradation are also summarized. The challenges and opportunities for the future development of stable and active SOC electrode microstructures are analyzed, and the corresponding prospects for commercial application are provided.