Abstract:With its high discharge capacity, ternary Ni-rich layered LiNixCoyMn1-x-yO2 (x≥0.6) materials have found an extensive application in many fields, however, the application in lithium-ion batteries is limited by its lithium-nickel mixed arrangement and poor structural stability. The ternary material LiNi0.6Co0.1Mn0.3O2 (NCM613) is modified by Nb2O5 coating, followed by an investigation of the influence of different coating amounts on the morphology, structure and electrochemical performance of NCM613, thus obtaining an optimum coating amount of 0.75%. The precursor LiNi0.6Co0.1Mn0.3O2(OH)2 is first prepared by co-precipitation method, followed by the preparation of the bare sample LiNi0.6Co0.1Mn0.3O2(NCM613)by adopting the high-temperature solid-phase method, with a final addition of Nb2O5 powders of different molar. Meanwhile coated samples with different ratios of Nb2O5@NCM613 are prepared by high temperature sintering and tempering after ball milling. An X-ray diffraction (XRD) study shows that there is a similarity between the crystal structure of the coated sample and the bare NCM613, both of which have a complete α-NaFeO2 layered structure with a low degree of cation mixing; SEM analysis shows that the coated sample and the bare NCM613 are both 1~1.5 μm-like spherical particles, with the elements of Ni, Co, Mn and Nb uniformly distributed on the surface of the spherical-like material. TEM analysis showed that the Nb2O5 coating thickness of 0.75Nb2O5@NCM613 is about 10~20 nm. The study of the electrochemical properties of the materials shows that the specific capacities of NCM613 and 0.75Nb2O5@NCM613 are 208.11 mA·h/g and 237.39 mA·h/g in the first cycle at current densities of 2.7~4.3 V and 0.2C, respectively. After 100 cycles at 1.0C, the discharge specific capacity of 0.75Nb2O5@NCM613 is 176.43 mA·h/g, with its capacity retention rate as high as 86%. Compared with the bare sample, there is a significant reduction of the impedance of 0.75Nb2O5@NCM613 after 100 cycles, with the electrochemical polarization reduced, and the reversibility enhanced as well, due to the fact that the Nb2O5 coating helps to improve the structural stability and electrochemical performance of the material. Therefore, Nb2O5-coated high-nickel ternary material is conducive to the promotion of the industrial production of high-nickel layered cathode materials.