A Rotating Cathode with Periodical Changes in Electrolyte Layer Thickness for High-Rate Li‒O 2 Batteries.

Li-O 2 batteries (LOBs) possess the highest theoretical gravimetric energy density among all types of secondary batteries, but they are still far from practical applications. The poor rate performance resulting from the slow mass transfer is one of the primary obstacles in LOBs. To solve this issue, a rotating cathode with periodic changes in the electrolyte layer thickness is designed, decoupling the maximum transfer rate of Li + and O 2 . During rotation, the thinner electrolyte layer on the cathode facilitates the O 2 transfer, and the thicker electrolyte layer enhances the Li + transfer. As a result, the rotating cathode enables the LOBs to undergo 58 cycles at 2.5 mA cm -2 and discharge stably even at a high current density of 7.5 mA cm -2 . Besides, it also makes the batteries exhibit a large discharge capacity of 6.8 mAh cm -2 , and the capacity decay is much slower with increasing current density. Notably, this rotating electrode holds great promise for utilization in other electrochemical cells involving gas-liquid-solid triple-phase interfaces, suggesting a viable approach to enhance the mass transfer in such systems.