Oxygen Redox In article number 2103384 Duho Kim, Seung-Ho Yu and co-workers improve the reversibility of oxygen redox in Li-excess Na layered oxides by Al3+ doping. The presence of an additional stable phase during the oxygen redox is a critical factor in extending and stabilizing the discharge capacity. In addition, redox-inactive Al3+ causes heterogeneous oxygen redox, which stabilizes the oxide framework under sensitively controlled oxygen participation upon cycling.