Breaking the Vicious Spiral to Suppress Oxygen Loss in Li-Rich Oxide Cathode Materials

The irreversible oxygen loss (O-loss) hinders the application of oxygen redox (O-redox) cathode material in high-energy-density Li/Na-ion batteries. Although O-loss is commonly associated with O₂ release, the underlying mechanism remains unclear, which is not a simple surface problem. Herein, the O-loss/redox behaviors of the layered Li₂MnO₃ and spinel Li₄Mn₅O₁₂ are comparatively investigated through experiments and density functional theory (DFT) calculations. It shows that the vicious spiral between O─O dimerization and Mn migration drive the void growth, chain-like structural collapse, and O₂ release in Li₂MnO₃. In contrast, the stable spinel framework and inert O in O-LiMn₃ coordination of Li₄Mn₅O₁₂ break this spiral and trap O₂ within the bulk, ensuring a reversible O-redox. By atomically compositing Li₄Mn₅O₁₂ with LiNi_0.5Mn_1.5O₄, a novel Co-free Li-rich spinel oxide (LRSO) with high energy density (>1000 Wh kg^-1) is produced. These findings clarify the correlation between structural rearrangement and O-redox and contribute to the design of advanced O-redox cathode materials.