Synthesis and characterization of advanced high capacity cathode active nanomaterials with three integrated spinel-layered phases for Li-ion batteries

Abstract

Mesoporous cathode active materials that included undoped and separated Cu2+ and Co3+ doped spinels were prepared. The "doped spinel-Layered-Li-rich spinel" composite nanoparticles within the three integrated phased (LiM(0,02)Mn(1,98)O(4)eLi(2)MnO(3)-Li1,27Mn1,73O4; where M is Cu2+ and Co3+) were synthesized by a microwave assisted hydrothermal synthesis. These materials were investigated with X-Ray powder Diffraction spectroscopy (XRD), Scanning Electron Microscopy (SEM and FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM), galvanostatic cycling at 0.1C and 0.5C rates, Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). The effects of the calcination temperature and the partial substitution of Mn3+ in the spinel by Cu2+ and Co3+, and onto the spinel structure were investigated with XRD. The lattice parameters of the spinel structured compounds were calculated from the XRD data using the Williamson-Hall equation. However, the morphological changes, which depended on the calcination temperature, were examined by SEM, FE-SEM and HRTEM. Furthermore, the two other phases which were different from LiM0,02Mn1,98O4 had a great impact on the electrochemical performance over the potential range of the 3-5 V. At the 0.1C rate, the first discharge capacities of undoped and Cu2+, Co3+ doped materials were 577, 285, 560 mAh/g respectively. After 50 cycles at 0.5C rate, we achieved 96.2%; 52.5%; 95.4% capacity retention for the undoped and Cu2+, Co3+ doped materials respectively. (C) 2016 Elsevier B.V. All rights reserved.