Recent Advances and Challenges in Perovskite-Based Protonic Ceramic Electrolytes: Design Strategies and Fabrication Innovations

Protonic ceramic electrochemical cells (PCECs) have received extensive research attention as full solid-state, electrochemical devices that can interconvert electrical and chemical energies via rapid proton conduction at reduced temperatures. Nonetheless, the practical application of PCECs still faces numerous challenges. In addition to the development of electrode materials, the protonic ceramic electrolytes (PCEs), which are crucial for the performance and stability of PCECs, encounter issues such as poor sinterability, low ionic conductivity, and inadequate thermochemical matching. To address these obstacles, the design and optimization of protonic ceramic electrolytes have recently become essential research focuses in the field of PCECs. To achieve effective customization of the elemental composition, crystal structure, defect structure, ionic conductivity, and chemical stability, many candidates for electrolyte materials with various compositions have been proposed. This review also covers state-of-the-art developments in PCE fabrication technologies, including powder synthesis, thin-film deposition, more controllable sintering processes and interface treatments for structural integrity and ionic conductivity. This review comprehensively summarizes the most recent design approaches and optimization strategies for perovskite-based protonic ceramic electrolyte materials and is crucial for advancing the commercialization of PCECs.