Li1.2Mn0.54Ni0.13Co0.13O2 hollow hierarchical microspheres with enhanced electrochemical performances as cathode material for lithium-ion battery application

Abstract

Li1.2Mn0.54Ni0.13Co0.13O2 hollow hierarchical microspheres (LNCM-HS) were successfully synthesized by molten salt method used the as-prepared MnO2 microspheres as the precursor and template. The sharp and well-defined reflection peaks suggest a high crystallization degree of the samples, and no impurities were observed. Li1.2Mn0.54Ni0.13Co0.13O2 material obtained is a solid solution consisting of rhombohedral R3-m and monoclinic C2/m group symmetries, which is confirmed by XRD, Raman spectra, and HRTEM. SEM and TEM shows that the hierarchical microspheres of LNCM-HS are composed of primary nano particles with the size of about 50nm. EDS mapping demonstrates that Ni, Mn, Co, and O elements are evenly distributed without any phase separation in LNCM-HS, and the atomic ratio of Mn, Co, Ni is calculated to be 0.54: 0.13: 0.12, which is quite close to the stoichiometry of 0.5 Li2MnO3·0.5LiMn1/3Co1/3Ni1/3O2. LNCM-HS exhibits excellent rate capacity of 309.9 (0.1C), 280.1 (0.3C), 226.5 (0.75C), 178.3 (1C), 139.3 (3C), and 101.0mAhg−1 (5C), respectively, whereas LNCM-bulk cathode displays a discharge capacity of 290.1, 230.0, 163.3, 135.4, 92.7, and 60.2mAhg−1 at the same rates. The improved capacity of LNCM-HS is ascribed to the increased lithium diffusion coefficient and reduced charge transfer resistance. The enhanced electrochemical performances can be attributed to the distinctive hollow microspheres structures, the increase contacting area between electrodes and electrolyte and the buffered volume changes during Li ions intercalation/deintercalation processes.