Adding a third spinel component, for example, LiNi0.5Mn1.5O4, to this layered-layered composite cathode has been proposed to allow a fast Li+ diffusion and to operate even at a higher voltage (>4.7 V vs. Li/Li+).6-9 Here, we have precisely controlled the mole ratio of C2/m Li2MnO3, R-3m LiNi0.5Mn0.3Ni0.2O2, and Fd-3m LiNi0.5Mn1.5O4 to form a closely-connected “layered-layered-spinel” composite cathode materials using a robust and efficient solid state high-energy ball-milling process.10 We have carried out both ex situ and synchrotron-based in situ x-ray diffraction (XRD) analysis and observe that there are less structural distortions during charge/discharge cycling.10 Furthermore, we carry out density functional theory (DFT) calculations with van der Waals (vdW) correction to explain reduced phase transformation and enhanced stabilization in the integrated cathode system that lead to a large and stable capacity of ~200 mAh g-1 operating at high voltages up to 4.9 V vs. Li/Li+.10
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This work was supported by Northwestern-Argonne Institute of Science and Engineering (NAISE). This work was also supported by the National Research Foundation of Korea Grant funded by the Korean Government (MSIP)" (NRF-2011-C1AAA001-0030538) and by KIST Institutional Program (Project No. 2E25303).
The 1st cycle charge/discharge profiles of layered-layered-spinel composite cathode materials consist of Li2MnO3, LiNi0.5Mn0.3Co0.2O2, and LiNi0.5Mn1.5O4 prepared with solid state high-energy ball-milling method. The scanning electron microscopy (SEM) images of the raw Li2MnO3, LiNi0.5Mn0.3Co0.2O2, and LiNi0.5Mn1.5O4 powders are provided. The chemical structures of the layered-layered composite cathode materials and the spinel Li1+xNi0.5Mn1.5O4 cathode compound are shown.