Despite the high-capacity nature of layered lithium Ni-rich oxide, achieving its universal implementation faces challenges due to the limitations in synthetic control. Minor variations in synthetic conditions lead to severe electrochemical performance degradation of Ni-rich cathodes. Thus, extensive studies have focused on the crystallographic structure through different synthetic routes; however, the electronic structure has been somewhat overlooked. Herein, we demonstrate the oxygen environment undergoes significant alterations based on synthetic conditions, resulting in detrimental drawbacks in cyclability. The correlation between crystal structure and oxygen redox activity, especially focusing on transition metal–oxygen (TM–O) covalency, is intensively studied through diffraction and spectroscopy analyses. Further combining with the model study by ab initio density functional theory calculation, we show that the origin of oxygen lability comes from the Li occupancy at the TM site, facilitating the participation of lattice oxygen during redox. This study provides crucial insights for the future design of Ni-rich cathodes, emphasizing the need to balance crystallographic and electronic structural considerations.