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 Cu 2+ and Co 3+ 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 –Li 2 MnO 3 –Li 1,27 Mn 1,73 O 4 ; where M is Cu 2+ and Co 3+ ) 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 Mn 3+ in the spinel by Cu 2+ and Co 3+ , 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 LiM 0,02 Mn 1,98 O 4 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 Cu 2+ , Co 3+ 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 Cu 2+ , Co 3+ doped materials respectively.