Synthesis and Characterization ofLiNi0.7–xMgxCo0.3O2(0≤x≤0.1) Cathode Materials for Lithium-Ion Batteries Prepared by a Sol-Gel Method

Abstract

Prospective cathode materialsLiNi0.7–xMgxCo0.3O2(0≤x≤0.1) for a lithium-ion secondary battery were synthesized using a sol-gel method. The structural and electrochemical properties were examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry(CV), and charge-discharge tests. The results show that theLiNi0.7–xMgxCo0.3O2maintains theα-NaFeO2type layered structure regardless of the magnesium content in the rangex⩽0.1. On the other hand, Mg-doping improves the capacity retention well. Besides, the Mg-doping promotes the diffusion of Li+in LiNi0.7Co0.3O2. Moreover, Mg-doping suppresses the phase transitions that usually occur in LiNiO2during cycling and improves the charge-discharge reversibility of Li/LiNi0.7Co0.3O2. High temperature cycling performance of the cathode at 55.5°C is also improved by Mg-doping, which is possibly attributed to the total stronger metal-oxygen bonding and the enhanced structure stability of those delithiated Mg-doped cathodes during cycling.