Potassium–Oxygen Batteries: Significance, Challenges, and Prospects

To mitigate a global crisis of Li depletion, potassium-based rechargeable batteries have received significant attention because of their low cost and high specific energy density. In particular, the rechargeable potassium oxygen (K–O 2 ) battery has been recognized as a promising energy storage technology because of its low overpotential and high round-trip efficiency based on the single-electron redox chemistry of potassium superoxide. Despite these merits, research on the development of K–O 2 batteries is still in its early stages owing to a lack of understanding of the fundamental reaction chemistry and the difficulties encountered in handling, in terms of practical acceptability. Hence, it is necessary to summarize the representative works and provide overall insights on K–O 2 batteries and recommendations for future studies. In this Perspective, we critically review the important scientific aspects of K–O 2 batteries, discuss the current challenges encountered, and provide recommendations from the scientific and practical points of view. We hope that this Perspecitve will be helpful in designing innovative and advanced K–O 2 batteries.