Investigation the electrochemical performance of Li1.2Ni0.2Mn0.6O2 cathode material with ZnAl2O4 coating for lithium ion batteries

Layered solid solution materials Li1.2Ni0.2Mn0.6O2 were synthesized with one sample heat treated and three other coated with ZnAl2O4 with varying amounts (0.5, 1 and 2.5 wt%) at high temperature. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effect of ZnAl2O4 coatings on the electrochemical performance of the pristine material was evaluated from charge/discharge cycles, rate performance, and electrochemical impedance spectroscopy (EIS). The results from TEM and selected area electron diffraction (SAED) indicate that the ZnAl2O4 coating assumes a spinel structure on the Li1.2Ni0.2Mn0.6O2. The discharge capacities and coulombic efficiencies of the Li1.2Ni0.2Mn0.6O2 materials in the first cycle are improved with the addition of ZnAl2O4. Li1.2Ni0.2Mn0.6O2 coated with 1 wt% ZnAl2O4 shows the highest discharge capacity (254.3 mAhg−1), highest capacity retention (98.6% for 50 cycles), and best rate capability (84 mAhg−1 at 10 C). EIS indicates that the resistance of Li1.2Ni0.2Mn0.6O2 electrodes decrease with the addition of ZnAl2O4 consistent with the excellent rate capability.