From K-O2 to K-Air Batteries: Realizing Superoxide Batteries on the Basis of Dry Ambient Air.

Although using an air cathode is the goal for superoxide-based potassium-oxygen (K-O2 ) batteries, prior studies were limited to pure oxygen. Now, the first K-air (dry) battery based on reversible superoxide electrochemistry is presented. Spectroscopic and gas chromatography analyses are applied to evaluate the reactivity of KO2 in ambient air. Although KO2 reacts with water vapor and CO2 to form KHCO3 , it is highly stable in dry air. With this knowledge, rechargeable K-air (dry) batteries were successfully demonstrated by employing dry air cathode. The reduced partial pressure of oxygen plays a critical role in boosting battery lifespan. With a more stable environment for the K anode, a K-air (dry) battery delivers over 100 cycles (>500 h) with low round-trip overpotentials and high coulombic efficiencies as opposed to traditional K-O2 battery that fails early. This work sheds light on the benefits and restrictions of employing the air cathode in superoxide-based batteries.