Spherical lithium-rich layered Li1.13[Mn0.534Ni0.233Co0.233]0.87O2 with concentration-gradient outer layer as high-performance cathodes for lithium ion batteries

Abstract

A spherical lithium-rich layered cathode material with an average composition of Li1.13[Mn0.534Ni0.233Co0.233]0.87O2 was successfully synthesized via co-precipitation route. In this material, each particle was consisted of an inner core and a stable concentration-gradient outer layer in which manganese content was gradually increased. The concentration-gradient material showed a typical rhombohedral LiNiO2-like layered structure with the existence of the monoclinic Li2MnO3-type integrated component. It can be found from the cross-sectional SEM images that the concentration-gradient particle was quite homogeneous without any apparent gap between the inner core and the concentration-gradient outer layer. Furthermore, according to the EDXS analysis, the concentrations of Mn, Ni, and Co kept almost constant throughout the core, and the concentration of Mn increased gradually within the outer layer of the particle. The lithium-rich layered material can deliver a very high capacity of 220 mAh g−1, and the excellent cycle life and improved thermal stability were achieved by the concentration-gradient outer layer. The results here indicate that the lithium-rich layered material with a manganese-rich concentration-gradient outer layer will be a promising cathode material for advanced lithium ion batteries with high capacity, long cycle life, and improved safety.