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 LiNi0.5Mn1.5O4, 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.