Despite their high electrocatalytic activity for oxygen electrode reactions, the low phase stability and high thermal expansion of perovskite structured materials have created difficulties in cell fabrication scale-up and long-term operational stability of reversible ceramic cells. Herein, an exceptionally high-performance electrocatalyst is presented based on a misfit-layered structure, Na0.15Ca2.85Co4O9–δ (NCCO). NCCO cells enable exceptional fuel cell performance down to 400 °C, with peak power densities of 0.18–5.15 W cm−2 at 400–800 °C, as well as electrolysis performance of minus current density 5.96–15.07 A·cm−2 (at 1.4 V) at 600–750 °C, exceeding the values of all previously described reversible (oxygen and proton) ceramic cells. Furthermore, the durability of NCCO cells is demonstrated for over 900 h at high current densities of 1 and 2 A cm−2 in fuel cells and –0.5 and –4 A cm−2 electrolysis cell modes under load cycle and constant current reversible operation, respectively. Doping with basic monovalent Na+ ions in the Ca-site in Ca3Co4O9+δ generates a high density of extra charge carrier species with the increased Co oxidation state and facilitates the proton uptake and diffusion properties of misfit-layered materials. This finding can deliver a new opportunity to develop innovative bifunctional oxygen electrode catalysts, while providing more favorable reaction pathways for the diffusion of charged species.