Synthesis of LiNi1-xCoxPO4/C nanocomposite cathode for lithium ion batteries by a combination of aerosol and powder technologies

摘要

Pure LiNi1-xCoxPO4 (x = 0, 0.2, 0.5, 0.8, 1) was synthesized by spray pyrolysis followed by heat treatment. The X-ray diffraction (XRD) patterns of LiNi1-xCoxPO4 were indexed to olivine structure with a Pnma space group. The peak shift and variation of lattice parameters suggested that LiNi1-xCoxPO4 solid solution was formed. Moreover, LiNi1-xCoxPO4/C (x = 0, 0.2, 0.5, 0.8, 1) nanocomposites were successfully synthesized by a combination of spray pyrolysis and wet ball milling followed by heat treatment. The XRD patterns of all samples were indexed to olivine structure with a Pnma space group. From scanning electron microscopy images, the primary particle sizes of LiNi1-xCoxPO4/C nanocomposites were reduced to the range of approximately 50-100 nm. LiNi0.5Co0.5PO4/C cathode exhibited a higher first discharge capacity and cyclability than those of pure LiNi0.5Co0.5PO4. Cyclic voltammetry data demonstrated that reduction peaks of LiNi0.5Co0.5PO4/C cathode occur at 4.44 V and 4.71 V, which were ascribed to Co3+/Co2+ and Ni3+/Ni2+ reduction couples, respectively. Electrochemical impedance spectroscopy data revealed that the LiNi0.5Co0.5PO4/C cathode had a smaller charge transfer resistance, resulting in a faster redox reaction kinetics for the lithium insertion and extraction, due to reduced particle size and introduced conductive carbon. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.