Abstract: Solid oxide electrolysis cells (SOECs) have attracted considerable attention in advanced energy conversion systems owing to their high energy conversion efficiency, versatile electrochemical functionalities, and potential for H₂O/CO₂ co-electrolysis. However, limited long-term durability remains a critical challenge restricting their widespread application. This work elucidates the formation mechanisms and spatial distribution of locally elevated oxygen chemical potential, as well as the conditions required for its transition into localized high oxygen pressure within the oxygen electrode/electrolyte interfacial region. Particular emphasis is placed on the degradation behaviors of different regions within SOECs under highly oxidizing conditions, including electrolyte defect evolution, interfacial crack propagation and mechanical delamination, as well as compositional evolution and structural reconstruction of oxygen electrodes. The correlations among local state evolution, multiscale structural degradation, and electrochemical performance decay are further discussed. Building upon these insights, stabilization strategies involving oxygen electrode material design, interface engineering, electrolyte regulation, microstructural optimization, and operational mode adjustment are summarized, with their advantages and limitations critically evaluated. Finally, future perspectives are discussed regarding the synergistic optimization of material systems, interfacial architectures, and operating strategies toward highly durable SOECs, offering insights into the development of high-performance electrolysis devices.

Key words: solid oxide electrolysis cells, oxygen chemical potential, oxygen electrode/electrolyte interface, multiscale degradation, review