Enhanced electrochemical performances of layered cathode material Li1.5Ni0.25Mn0.75O2.5 by coating with LiAlO2

Layered solid solution cathode Li1.5Ni0.25Mn0.75O2.5 has been synthesized and coated by composite oxides LiAlO2 with varying amounts (1, 3, 5 and 8 wt%) in this paper. The effect of coated LiAlO2 on the physical and electrochemical properties of the material has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), discharge, cyclic performance, rate capability and electrochemical impedance spectroscopy (EIS). The discharge capacity and coulombic efficiency of Li1.5Ni0.25Mn0.75O2.5 in the first cycle have been improved after LiAlO2 coating. And the 5 wt% LiAlO2 coated Li1.5Ni0.25Mn0.75O2.5 shows the best discharge capacity (257.6 mA h g−1), capacity retention (101.6% for 50 cycles) and rate capability (88.3 mA h g−1 at 10 C). Electrochemical impedance spectroscopy (EIS) results show that the Rct of Li1.5Ni0.25Mn0.75O2.5 electrode decreases after LiAlO2 coating, which is due to high lithium ion diffusion coefficient of LiAlO2, is responsible for superior rate capability.