Solid-state Li-O 2 batteries possess the ability to deliver high energy density with enhanced safety. However, the challenge to design a high-functioning solid-state air electrode becomes the main bottleneck for its further development due to the presence of multiple solid-state interfaces, limiting the electron/ion exchange and resulting in poor electrochemical performance. Herein, we propose to adopt a hybrid electronic and ionic conductor to build solid-state air electrode that makes the transition of Li-O 2 battery electrochemical mechanism from a three-phase process to a two-phase process. As a result, the solid-state Li-O 2 battery with this hybrid conductor solid-state air electrode exhibits dramatically decreased interfacial resistance and significantly enhanced reaction kinetics. More importantly, the Coulombic efficiency of Li-O 2 battery is also significantly improved benefiting from the good contact between discharge products and electrode materials. In-situ environmental transmission electron microscopy under an oxygen ambiance was used to vividly illustrate the reversible deposition and decomposition of discharge products on the surface of this hybrid conductor, visually verifying the fact of the two-phase reaction.