The effects of molybdenum doping on LiNi_0.6Co_0.2Mn_0.2O₂ cathode material

The high valence and large ionic radius of Mo⁶⁺ is selected as a dopant to modify the LiNi_0.6Co_0.2Mn_0.2O₂ material through the molecular level mixed calcination method. The Mo⁶⁺ substitutes the transition metal atoms in the material proportionately, which has no influence on the original atom ratio of the transition metal, and may expand the Li⁺ diffusion pathways. The strong bond energy of Mo-O benefits the stability of the material. Meanwhile the electrochemical reaction of Mo⁶⁺/Mo⁴⁺ in the process of charging and discharging might increase the capacity of the material. The electrochemical impedance spectroscopy clearly demonstrates that the Mo-doping reduces the charge transfer impedance and enhances the electrochemical reaction activity of the lithium ion. When x = 0.01, the material shows an excellent cycling and rate performance. The discharge specific capacity can reach up to 208 mAh g⁻¹ at 0.2C under 2.8 V–4.6 V, and remains 75% of the first discharge capacity after 101 cycles, which is 10% higher than the un-doped material.