Single O Hole Enables High Cycling Performance by Removing Thermodynamic and Kinetic Limitations

Abstract

Lithium-rich layered oxides involving both transition metal and oxygen redox have received widespread attention due to their high energy density. However, the participation of oxygen redox in charge compensation generally leads to significant voltage decay and capacity fade, largely because of the dimerization of lattice oxygen. Therefore, tunability and stabilization of O redox configuration become crucial. In this study, the stability of the multiple forms of oxygen redox and the resulting role in cycling performance have been comparatively studied. A stabilized single O hole state has been identified experimentally for the first time not only in the first cycle but also in the long term cycle, in sharp contrast to the case of O dimer. Moreover, the superiority of the O hole can also be reflected in removing kinetic limitations. These findings may open new horizons for offering stable and high capacity via regulation of specific oxygen-redox forms.