Researchers at the Institute of Science Tokyo have identified a rare rubidium-containing oxide-ion conductor, Rb₅BiMo₄O₁₆, which exhibits exceptionally high conductivity and stability. This discovery, achieved through computational screening and experiments, showcases the potential of rubidium in advancing oxide-ion conductor technology. The research team's systematic approach led to the selection of Rb₅BiMo₄O₁₆ based on its low activation energy, large free volume, and structural features, making it a promising candidate for solid oxide fuel cells. The material demonstrated outstanding oxide-ion conductivity, surpassing yttria-stabilized zirconia, and exhibiting remarkable stability under various conditions, including high temperatures and exposure to different gases. This breakthrough could revolutionize the development of oxide-ion conductors, potentially lowering the operating temperature and costs of solid oxide fuel cells. The findings open up new avenues for the application of rubidium in clean energy technologies and highlight the significance of innovative materials in advancing sustainability-focused energy solutions.