TiO2-coated LiNi0.9Co0.08Al0.02O2 cathode materials with enhanced cycle performance for Li-ion batteries

Abstract

Ni-rich cathode material is one of the most promising materials for Li-ion batteries in electric vehicles. However, fading capacity, poor cyclic stability and high pH value are still major challenges, which suppress its practical application. In this study, spherical LiNi0.9Co0.08Al0.02O2 powders with 0.4 wt% TiO2 coating layer were prepared by impregnation–hydrolysis method. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) results show that TiO2 is uniformly coated on the surface of LiNi0.9Co0.08Al0.02O2 particle and slightly embedded into LiNi0.9Co0.08Al0.02O2 particles. After 100 cycles at 2.0C, 0.4 wt% TiO2-coated LiNi0.9Co0.08Al0.02O2 electrode delivers much higher discharge capacity retention (77.0%) than the pristine LiNi0.9Co0.08Al0.02O2 electrode (63.3%). The excellent cycling performance of 0.4 wt% TiO2-coated LiNi0.9Co0.08Al0.02O2 electrode at a high discharge ratio is due to a TiO2 coating layer which can effectively reduce the direct contact between cathode material and electrolyte, suppress the oxidation of electrolyte, improve electrical conductivity of the electrode and increase the stability of the structure. With the increase of current density, TCNC sample clearly exhibits enhanced cycling performance with higher capacity retention, and the capacity retention of TCNC increases by 22% at 2.0 C.