Improvement of the electrochemical performance of LiNi0.33Mn0.33Co0.33O2 cathode material by chromium doping

LiNi0.33Mn0.33-x Co0.33Cr (x) O-2 (x=0, 0.01, 0.025, 0.05) materials were synthesized by Cr3+ substitute of Mn4+ to enhance their electrochemical properties. The structure and electrochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge/discharge tests. The materials maintained the alpha-NaFeO2 type layered structure and the discharge capacities were also increase by doping appropriate amount of Cr3+. The sample with x = 0.025 exhibited the highest discharge capability of 181.6 mAh g(-1) and the best cycle performance. EIS measurement showed that the Cr-doped electrode had the lower resistance impedance increase during cycling. The chemical diffusion coefficient of Li+ ion (D (Li)) was measured by potentiostatic intermittent titration technique (PITT). The result showed that D (Li) in Cr-doped electrode was faster than that of the un-doped one.