Oxygen ions, which migrate through the electrolyte, participate in chemical reactions at the three-phase interface where they meet the air electrode, producing oxygen gas. Electrons are transferred via the air electrode. However, some oxygen ions that do not engage in the chemical reactions accumulate within the electrolyte. These accumulated oxygen ions deform the atomic structure of the electrolyte, leading to the formation of nano defects and subgrains, which eventually cause cracks in the solid oxide electrolysis cell.

Using electron beam diffraction analysis with advanced TEM, the research visually confirmed the stress formed at the electrolyte interface. Additionally, density functional theory (DFT) was used to reveal the phenomenon of reduced atomic distances resulting from the accumulation of oxygen ions.