Dynamic oxygen shield eliminates cathode degradation in lithium-oxygen batteries

Realizing a reversible and long-life nonaqueous lithium-oxygen (Li-O-2) battery has been proven extremely challenging due to reactive reaction products/intermediates that rapidly corrode and passivate the cathode. In this work, we effectively protect the cathode from oxygenated side reactions by manipulating the fluxes of reduced discharge mediator (rDM) and O-2, thereby creating a steady-state rDM-rich region which completely covers the cathode. This rDM-rich region acts as a dynamic O-2 shield and isolates the cathode from oxygen reactions. We demonstrate that this strategy eliminates 98% of the by-products on the cathode, achieving a more than 10-fold increase in cycle life compared to conventional dual-mediator cells. A diffusion-reaction model is developed to assist understanding of the system and to guide future design. This work demonstrates an effective approach to achieve degradation-free cathodes for efficient and long-life Li-O-2 batteries.