Self‐Compressive Stress Promoting Densification of Proton‐Conducting Electrolyte Membranes

Abstract Dense asymmetric ceramic membranes are key components in solid oxide cells (SOCs) and gas separation technologies. In particular, proton‐conducting SOCs efficiently generate power and hydrogen at low temperatures. However, high‐temperature sintering of these membranes causes elemental volatilization, segregation, and migration, significantly reducing the protonic conductivity of the electrolyte layer (e.g., BaCe 0.7 Zr 0.1 Y 0.2 O 3‐δ (BCZY712)) and limiting cell performance. Here we report a self‐compressive stress strategy to promote densification of a BCZY712 proton‐conducting electrolyte layer. By precisely regulating the pore former content and the pre‐sintering temperature of the anode substrate which shrinks more than the electrolyte layer, a compressive stress is applied to the electrolyte layer. Under the compressive stress, the densification temperature decreased by ∼150 °C, achieving a relative density of ∼99%. The reduced co‐sintering temperature effectively suppresses barium evaporation, Y 2 O 3 impurity segregation, and Ni migration from the anode substrate to the electrolyte. Consequently, the electrolyte exhibits a markedly 151%‐higher conductivity and the cell delivers an 89%‐improved peak power density compared to a cell co‐sintered at conventional high‐temperature.