Bismuth oxide electrolytes with superior conductivity and stability

Double-doping bismuth oxide led to record high conductivity in both cubic and rhombohedral structures. • Developed highest oxygen-ion conductivity phase-stable oxides. • Achieved by optimizing average dopant radii in double-doped bismuth oxide. • Enables higher performance applications from oxygen generation to energy conversion and storage. Higher conductivity electrolytes are imperative for the reduction of operating temperature and increased viability of numerous solid-state oxygen-ion conducting technologies. Unfortunately, the highest oxygen ion conducting electrolyte, doped cubic bismuth oxide, is only useable above 600 °C due to anion ordering below this temperature. Reported herein, we have tailored the structure of the bismuth oxide electrolyte to allow functionality at both high and low temperatures. At higher temperatures (≥600 °C), we have demonstrated a cubic Bi 2 O 3 with the highest oxygen-ion conductivity ever recorded for a phase stable (demonstrated for 100 h of operation at 650 °C) electrolyte. Meanwhile, at lower temperatures (<600 °C), a rhombohedral Bi 2 O 3 electrolyte was developed with exceptional stability, exhibiting no observable conductivity decay for 100 h of aging at 500 °C, thus making it the highest oxygen ion conducting electrolyte with stable performance for lower temperature solid oxide cells (SOCs).