Abstract:The layered LiNi_0.6Co_0.2Mn_0.2-yMg_yO_2-zF_z (0≤y≤0.12, 0≤z≤0.08) cathode materials were synthesized by combining co-precipitation method and high temperature solid-state reaction, with the help of the ball milling, to investigate the effects of F-Mg doping on LiNi_0.6Co_0.2Mn_0.2O₂. Compared with previous studies, this doping treatment provides substantially improved electrochemical performance in terms of initial coulombic efficiency and cycle performance. The LiNi_0.6Co_0.2Mn_0.11Mg_0.09O_1.96F_0.04 electrode delivers an high capacity retention of 98.6% during the first cycle and a discharge capacity of 189.7 mA·h/g (2.8-4.4 V at 0.2C), with the capacity retention of 96.3% after 100 cycles. And electrochemical impedance spectroscopy(EIS) results show that Mg-F co-doping decreases the charge-transfer resistance and enhances the reaction kinetics, which is considered to be the major factor for higher rate performance. It is demonstrated that LiNi_0.6Co_0.2Mn_0.11Mg_0.09O_1.96F_0.04 is a promising cathode material for lithium-ion batteries for excellent electrochemical properties.

Key words: nickel-rich cathode material; F-Mg doping; high columbic efficiency; cycling stability