Synthesis and characterization of LiCo0.3−xGaxNi0.7O2 (x = 0, 0.05) as a cathode material for lithium ion battery

The single phase of LiCo0.3−xGaxNi0.7O2 (x = 0, 0.05) was synthesized by a sol–gel method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance. The powders are homogeneous and have a good-layered structure. The synthesized LiCo0.25Ga0.05Ni0.7O2 exhibits better electrochemical performance with an initial discharge capacity of 180.0 mAh g−1 and a capacity retention of 95.2% after 50 cycles between 2.8 and 4.4 V at 0.2C rate. The study on the structural evolution of the material during the cycling shows that Ga-doping improves the structure stability of LiCo0.3Ni0.7O2 at ambient temperature and 55 °C. Meanwhile, Ga-doping not only suppresses the alternating current (AC) impedance of LiCo0.3Ni0.7O2 but also promotes the Li+ diffusion in LiCo0.3Ni0.7O2. Furthermore, thermal stability of the charged LiCo0.25Ga0.05Ni0.7O2 is improved, which may be attributed to the retard of O2 evolution in LiCo0.3Ni0.7O2 and the suppression of electrolyte oxidation during cycling by Ga-doping.