Structurally robust lithium-rich layered oxides for high-energy and long-lasting cathodes.

O2-type lithium-rich layered oxides, known for mitigating irreversible transition metal migration and voltage decay, provide suitable framework for exploring the inherent properties of oxygen redox. Here, we present a series of O2-type lithium-rich layered oxides exhibiting minimal structural disordering and stable voltage retention even with high anionic redox participation based on the nominal composition. Notably, we observe a distinct asymmetric lattice breathing phenomenon within the layered framework driven by excessive oxygen redox, which includes substantial particle-level mechanical stress and the microcracks formation during cycling. This chemo-mechanical degradation can be effectively mitigated by balancing the anionic and cationic redox capabilities, securing both high discharge voltage (~ 3.43 V vs. Li/Li⁺) and capacity (~ 200 mAh g⁻¹) over extended cycles. The observed correlation between the oxygen redox capability and the structural evolution of the layered framework suggests the distinct intrinsic capacity fading mechanism that differs from the previously proposed voltage fading mode. O2-type Li-rich layered cathodes suppress voltage decay and aid in oxygen redox research. Here, the authors report trilateral relationship among anionic redox utilization, bulk chemo-mechanical degradation, and electrochemical fading, which can be mitigated by balancing the redox center capabilities. [ABSTRACT FROM AUTHOR]