High-entropy BCZGLY as a proton-conducting electrolyte: material-level validation and implications for electrochemical cells

The development of a resilient economy requires advanced electrochemical technologies for efficient power generation and storage, together with materials that reduce reliance on noble and critical raw materials. High-entropy materials offer a promising strategy to meet these demands. Here, we report a high-entropy perovskite electrolyte, BaCe 0.2 Zr 0.2 Gd 0.2 La 0.2 Y 0.2 O 3−δ (BCZGLY), designed to enhance chemical robustness and sinterability while retaining proton conductivity at intermediate temperatures. BCZGLY forms a single-phase perovskite and achieves improved densification at 1400 °C. Under humid atmospheres, conductivities of 54 mS cm −1 at 500 °C and 0.71 S cm −1 at 700 °C are obtained, comparable to state-of-the-art BaZr 0.8 Y 0.2 O 3−δ under similar conditions. Thermogravimetric and structural analyses reveal enhanced resistance to carbonation and controlled hydration, consistent with a stabilized defect landscape. First-principles calculations support a proton-friendly defect chemistry. Overall, these results identify BCZGLY as a promising electrolyte for intermediate-temperature protonic devices, while device-level validation is reserved for future studies and practical electrochemical applications. • High-entropy BCZGLY is introduced as a robust proton-conducting electrolyte. • High proton conductivity is sustained between 500 and 700 °C. • Combined DFT and experiments reveal a proton-friendly defect chemistry.