Suppressing Mn Reduction of Li-Rich Mn-Based Cathodes by F-Doping for Advanced Lithium-Ion Batteries

The Li-rich Mn-based cathode (LMR) has been considered as the most promising candidate for the next-generation secondary lithium-ion batteries. However, it suffers from structure degradation and oxygen release during cycling. To address this problem, a Li[Li_0.133Mn_0.467Ni_0.2Co_0.2]O_1.95F_0.05 cathode material was synthesized via polyacrylamide-assisted carbonate coprecipitation. With the partial replacement of an oxygen-metal (M-O) bond with a fluorine-metal (M-F) bond, the initial columbic efficiency, cycle performance, and voltage degradation have been improved effectively. In situ X-ray diffraction upon heating reveals that the structure stability of LMR can be improved by F-doping. The charge compensation of F-doped LMR is revealed by X-ray absorption spectroscopy during cycling. It is found that Mn reduction upon cycling can be suppressed effectively by F-doping in LMR. These results provide an in-depth understanding of F-doping effect on the optimization of Li-rich cathode materials for advanced lithium-ion batteries.