Synthesis and electrochemical properties of Mg-doped LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials for Li-ion battery

Abstract

The layered LiNi_0.6Co_0.2−xMn_0.2Mg _xO₂ (x=0.00, 0.03, 0.05, 0.07) cathode materials were prepared by a co-precipitation method. The properties of the Mg-doped LiNi_0.6Co_0.2Mn_0.2O₂ were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that the Mg-doped LiNi_0.6Co_0.2Mn_0.2O₂ had the same layered structure as the undoped LiNi_0.6Co_0.2Mn_0.2O₂. The SEM images exhibited that the particle size of Mg-doped LiNi_0.6Co_0.2Mn_0.2O₂ was finer than that of the undoped LiNi_0.6Co_0.2 Mn_0.2O₂ and that the smallest particle size is only about 1 μm. The Mg-doped LiNi_0.6Co_0.2Mn_0.2O₂ samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Mg was that x= 0.03 in the LiNi_0.6Co_0.2−xMn_0.2Mg _xO₂ samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility and electronic conductivity was enhanced, and the charge transfer resistance was decreased through Mg-doping. The improved electrochemical performances of the Mg-doped LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials are attributed to the addition of Mg²⁺ ion by stabilizing the layer structure.

Keywords

lithium ion batteries / LiNi_0.6Co_0.2Mn_0.2O₂ / Mg-doping / cyclic voltammogram (CV)

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