Concentration-gradient of Li-rich Mn-based cathode materials with enhanced cycling retention

Abstract

Lithium-rich layered Mn-based materials have attracted much attention because of their high specific capacity and high energy density, but they have the characteristics of irreversible capacity loss, low initial coulombic efficiency, and poor cycling performance. In this study, a core-shell structure, including Mn0.75Ni0.25C2O4 precursor as core and Li-rich Mn-based oxides (LRMO, Li1.2Mn0.54Ni0.13Co0.13O2) as shell layer respectively, was synthesized by co-precipitation and sol-gel method. After sintering at high temperatures, the element concentration-gradient oxides material (LRMO-G) was formed. The material was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) and its electrochemical performance was investigated by various electrochemical methods. The LRMO-G material exhibits a high initial discharge specific capacity of 268 mAh/g at 0.1 C, and extremely superior capacity retention (95.4 %) after 100 cycles at 1 C. The initial coulomb efficiency of the LRMO-G material increases to 85 %, which is 12 % higher than that of LRMO.