In this report, we demonstrate that a uniform angstrom-level oxide overcoat (either ceria or yttria with a nominal thickness of 0.7–1.5 Å) by atomic layer deposition is highly effective not only in enhancing the thermal stability of underlying infiltrated ceria nanoparticles but also in facilitating electrode kinetics. By employing Sr-free electrodes and Cr-free gas environment, we focus on the thermal agglomeration as the major degradation pathway and reveal the close correlation between thermal agglomeration rate of infiltrated nanoparticles and degradation rate of electrode performance in a quantitative manner. We also provide a mechanistic perspective on the beneficial effect of the overcoat in durability and performance of solid oxide fuel cell cathodes.