Effect of Ti4+ doping on LiNi0.35Co0.27Mn0.35Fe0.03O2

Li(Ni0.35Co0.27Mn0.35Fe0.03)(1-x)TixO2 (x = 0.00, 0.01, 0.02, 0.03, 0.04) cathode materials have been synthesized via hydroxide co-precipitation method followed by a solid state reaction. The crystal structure features, morphology, and electrochemical performances of the powders were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), charge/discharge test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results of XRD demonstrate that Ti-doping does not destroy the crystal structure, but can decrease cation ordering level and improve structural integrity. It can be seen from the SEM diagram that the particle size of Li(Ni0.35Co0.27Mn0.35Fe0.03)(0.98)Ti0.02O2 is more uniform and there is no obvious agglomeration. The results show that Li(Ni0.35Co0.27Mn0.35Fe0.03)(0.98)Ti0.02O2 has excellent electro-chemical performance. The average discharge capacity of Li(Ni0.35Co0.27Mn0.35Fe0.03)(0.98)Ti0.02O2 is higher than those of other materials at each rate. Li(Ni0.35Co0.27Mn0.35Fe0.03)(0.98)Ti0.02O2 has good cyclic stability, the first discharge capacity is 200.4 mAh/g, the diffusion coefficient of lithium ion is two orders of magnitude higher than that of pure phase, and the electrochemical properties are stable. Initial discharge specific capacity of Li (Ni0.35Co0.27Mn0.35Fe0.03)(0.98)Ti0.02O2 is 130.9 mAh/g at 1C, and the capacity retention rate after 50 cycles is 84.3%.