Facilitating structural stability of the Li-rich layered cathode materials by cation rearrangements and Li vacancies

Abstract

The anomalously high capacities of Li-rich materials are a result of contributions from both cationic and anionic redox processes, however, anionic redox also leads to capacity loss and structural degradation. In this study, the content of Li-O-Li configuration and the types of Li-O-TM configuration are regulated by introducing the Li deficiencies and changing the ratio of Ni/Co/Mn. The results of XRD, Raman spectra, XPS, HR-TEM and in-situ XRD characterizations indicate that the generation of the spinel structure and crystal defects strengthen the structural stability in the modified Li-rich materials. Besides, the density functional theory (DFT) calculation result prove that increasing the ratio of Ni/(Co+Mn) further enhance the electron contribution of the Ni ions and the electronic conductivity of as-prepared samples. The LR1.8–811 sample presents outstanding cycling performance and energy density, that is, the capacity retention is 98.64% and energy density is 764.7 Wh kg−1 after 100 cycles at a rate of 0.2C, respectively. These improvements are ascribed to the less content of Li-O-Li configuration and the more content of Li-O-Ni configuration in the LR1.8–811 material, which mitigated the oxygen redox and enhanced the structural stability.