Triggering and Stabilizing Oxygen Redox Chemistry in Layered Li[Na_1/3Ru_2/3]O₂Enabled by Stable Li-O-Na Configuration

Li-rich layered oxides are promising cathode candidates for high-energy-density Li-ion batteries because of the combination of cationic and anionic redox activities. However, severe lattice oxygen loss inevitably induces irreversible Li migration in both transition metal (TM) and Li layers, which degrades the stability of the Li-O-Li configuration, resulting in serious structure distortion and capacity decay. Herein, a Li-O-Na configuration was first introduced in Li-based layered oxides by Na substitution within TM layers, which not only obtained a discharge capacity of 232 mAh g-1 boosted by oxygen redox reactions but also achieved superior structural and electrochemical stability upon cycling (capacity retention of 83.2% after 1000 cycles). Moreover, comprehensive analyses of anionic/cationic redox activities clarify the underlying charge compensation mechanisms upon cycling. Altogether, these findings demonstrated that the Li-O-Na configuration can be regarded as an effective structure to achieve stable oxygen redox chemistry within Li-based cathode materials.