Preparation of LiCoO2 concaved cuboctahedra and their electrochemical behavior in lithium-ion battery

Abstract

LiCoO₂ concaved cuboctahedra with a size of about 1.0 μm were hydrothermally prepared from CoCO₃ and LiOH·H₂O at 150 °C. Field-emitting scanning electron microscope (FESEM) images show that the cuboctahedra consisted of four hexagonal plates, with angles of 70.5° in neighboring plates. Electron diffraction (ED) patterns of the hexagonal plates show 1 0 0 diffraction of LiCoO₂ in rhombohedral phase and 2 2 0 diffraction in spinel phase, which means LiCoO₂ concaved cuboctahedra are comprised of two intergrown phases. The electrochemical performance of these concaved cuboctahedra of LiCoO₂ at a rate of 0.5 C demonstrated first run charge/discharge capacities of 155 and 141 mAh g⁻¹ and a stable discharge capacity of 114 mAh g⁻¹ after 100 cycles. After that, FESEM images show the LiCoO₂ concaved cuboctahedra have undergone no significant change. At a temperature of 120 °C and under the same conditions, only a small amount of LiCoO₂ concaved cuboctahedron appeared. As the temperature rose to 180 °C, flower-like LiCoO₂ microstructures with a size of about 1.0 μm were formed, constructed of irregular plates. The electrochemical performance of the products prepared at 120 °C and 180 °C indicates lower stability than that of LiCoO₂ concaved cuboctahedra.