Thermal Swing Regeneration of Li-Air Battery Cathodes: A Practical Compromise for Prolonged Cyclic Performance

Lithium-air or lithium-oxygen battery, one of the strongest energy storage candidates for extended-range electric vehicles, has theoretical specific energy much greater than that of Li-ion battery. Efforts are underway to overcome the major obstacle of its capacity fades with discharge-charge cycles caused by the formation of the reaction products that are either electrically insulating or electrochemically irreversible. The most certain way to improve the cycle performance is to prevent the unfavorable products from forming from the beginning. However, no one hitherto has discovered a way to completely eliminate them while conducting the discharge-charge cycles. In this work, we present a pathbreaking way of utilizing the unavoidable and undesirable reaction products as catalytic "highways" for oxygen to infiltrate deeper inside the air cathode. Once the cathodes are used and become inactive, we bring them back to life by removing all the residual solvent under mild heat treatment, followed by selectively refilling the pores of the unpassivated carbon with the same electrolyte at room temperature. This so-called thermal swing regeneration process has brought a huge improvement of doubling the cycle life of lithium-air batteries, a better understanding of the intrinsic properties of three-phase interface present to all metal-air system, and provided a new insight towards pulling out full capacity of the system by complete utilization of the available carbon surface in the air cathode.