Enhanced electrochemical performances of layered cathode material Li_1.5Ni_0.25Mn_0.75O_2.5 by coating with LiAlO₂

Highlights: • Li_1.5Ni_0.25Mn_0.75O_2.5 powders are coated by LiAlO₂ with different amounts. • The electrochemical properties of Li_1.5Ni_0.25Mn_0.75O_2.5 are improved after coating. • The capacity retention of coated Li_1.5Ni_0.25Mn_0.75O_2.5 is improved from 90.8% to 101.6% after 50 cycles. - Abstract: Layered solid solution cathode Li_1.5Ni_0.25Mn_0.75O_2.5 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 Li_1.5Ni_0.25Mn_0.75O_2.5 in the first cycle have been improved after LiAlO₂ coating. And the 5 wt% LiAlO₂ coated Li_1.5Ni_0.25Mn_0.75O_2.5 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 R_ct of Li_1.5Ni_0.25Mn_0.75O_2.5 electrode decreases after LiAlO₂ coating, which is due to high lithium ion diffusion coefficient of LiAlO₂, is responsible for superior rate capability