Dual-site Doping to Enhance Oxygen Redox and Structural Stability of Li-rich Layered Oxides

Cobalt-free Li-rich layered oxides (LLOs) such as Li1.2Mn0.6Ni0.2O2 have attracted extensive attention owing to their high specific capacity and low cost. Nonetheless, numerous problems such as continuous voltage fading and capacity decay have become stumbling blocks in its commercial application. In this study, we propose an effective dual-site doping strategy by choosing Mo as the cation and F as the anion to enhance the capacity and cycling performance. The research demonstrates that the cycling stability of LLOs enhances with the doping ratio of Mo, and their capacity increases with the doping ratio of F. It is because Mo as a pillar enhances the structural stability and F doping is conducive to the activation of Li2MnO3. What's more, dual-site doping also promotes the diffusion of Li+ and reduces the internal resistance of the electrode. Due to these improvements, the 5F3M sample still maintains a discharge capacity of 190.98 mAh g(-1) after 100 cycles at 200 mA g(-1), which is much higher than 165.29 mAh g(-1) of the Pristine sample. This discovery provides a new way to develop advanced layered oxide cathodes for both Na- and Li-ion batteries.