Structural stability and enhanced electrochemical performance of Co-free Li-rich layered Mn-based Li 1.2 Mn 0.6 Ni 0.2 O 2 cathodes via F doping at the O site of lithium-ion batteries

Li-rich Mn-based Co-free layered oxides (LLOs) are promising cathode materials for lithium-ion batteries (LIBs). However, they exhibit capacity loss and low initial Coulombic efficiency. Herein, an F-doped Li 1.2 Mn 0.6- Ni 0.2 O 1.9 F 0.10 material has been prepared by the high-temperature solid-state method, with numerous oxygen vacancies on the surface to accelerate Li + transport. The electrochemical performance of Li 1.2 Mn 0.6 Ni 0.2 O 1.9 F 0.10 considerably improved after the treatment. A high-capacity retention of 86.9 % after 100 charge/discharge cycles at 1C was achieved for Li 1.2 Mn 0.6 Ni 0.2 O 1.9 F 0.10 . Results revealed that F doping replaces part of O2-, forming more force between the TM-F bonds (compared to the TM-O bond), which inhibits the cation mixing phenomenon. The layered structure stability of the material is improved after F doping, and the migration energy barrier of Li+ is reduced, which promotes the migration of Li+, thereby improving the electrochemical performance of Li 1.2 Mn 0.6 Ni 0.2 O 2 .