Effect of Structural and Electrochemical Properties of Yttrium-doped LiNi0.90Co0.05Al0.05O2 Electrode by Co-precipitation for Lithium Ion-batteries

In this study, the LiNi0.90−xCo0.05Al0.05YxO2 (x = 0, 0.025, 0.075) have been synthesized by a co-precipitation and solid-state reaction method. The effect of the Y3+-doping on the structural and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and by electrochemical and impedance spectroscopy (EIS). From the results of the XRD pattern changes between before and after the doping, less cation mixing and more ordered hexagonal structure were observed for the LiNi0.875Co0.05Al0.05Y0.025O2 cathode and the cell delivered an initial discharge capacity of 195.8 mAhg-1 and was 10.2 mAhg-1 higher than the pristine cell by yttrium doping effect. High rate capability studies were also performed and showed the capacity retention of 95, 81.7 and 63.8 % at 0.2, 1.0 and 5.0 C-rate, respectively during the cycling. The impedance spectra showed that the charge transfer resistance for the pristine cathode grew significantly, while that for the Y3+-doped cathode decreased during cycling. It was concluded that the capacity fading for LiNi0.90Co0.05Al0.05O2 mainly due to the cation mixing, partially contributed by the impedance growth and by doping the pristine material with Y3+, cation mixing can be efficiently suppressed, which results in the improved rate capability.