Preparation and Electrochemical Performance of Mg-Doped LiNi<sub>0.4</sub>Co<sub>0.2</sub>Mn<sub>0.4</sub>O<sub>2</sub> Cathode Materials by Urea Co-Precipitation

Abstract

The Mg-doped LiNi0.4Co0.2-xMn0.4MgxO2 cathode materials (x=0, 0.01, 0.02 and 0.03) were synthesized by a urea co-precipitation method. Its structure and electrochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical performance tests. XRD studies indicate that the Mg-doped LiNi0.4Co0.2Mn0.4O2 samples perform the same layered structure as the undoped LiNi0.4Co0.2Mn0.4O2. SEM images show that the particle size of Mg-doped LiNi0.4Co0.2Mn0.4O2 is smaller than the undoped LiNi0.4Co0.2Mn0.4O2 sample. Charge-discharge tests confirm that the rate capacity and cycling performance of LiNi0.4Co0.2-xMn0.4MgxO2 are improved by Mg-doped. The optimal doping content of Mg is x=0.02 in the LiNi0.4Co0.2-xMn0.4MgxO2 samples, which can achieve high initial charge-discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Mg-doping. The improved electrochemical performances of the Mg-doped LiNi0.4Co0.2Mn0.4O2 cathode materials are attributed to the addition of Mg2+ ion by stabilizing the layered structure.