Synthesis and Electrochemical Properties of Yb-Doped LiMnNiCoO₂ Cathode Materials Obtained by Sol-Gel Method.

The Li1.20[Mn0.54Ni0.13Co0.13]0.80-xYbxO2 (x = 0, 0.01, 0.02, 0.03) cathode materials have been synthesized by using sol-gel method and characterized by means of XRD, SEM, ICP-OES analysis. The galvanostatic charge-discharge tests results showed the improved electrochemical properties were obtained through the Yb3+ doping modification. With the increase of Yb3+ doping content, the capacity retentions enhanced from 85.6% to 88.9% and then decrease to 86.5% after 100 cycles with x = 0.01, 0.02 and 0.03, respectively, while the un-doped sample delivered the capacity retention of 83.0%. Besides, the discharge capacity of Li1.20 [Mn0.54Ni0.13Co0.13]0.78Yb0.02O2 was about 23.1 mAh g-1 larger than that of un-doped sample at 5C high rate. The electrochemical impedance spectroscopy (EIS) and cyclic voltammetric results indicated that the Yb3+ doping modification could suppress the layered-spinel phase transformation during cycling and maintain a lower value of charge transfer impedance.