Single crystal synthesis, crystal structure and electrochemical property of spinel-type LiCoMnO4 as 5 v positive electrode materials

Abstract

Micrometer-sized single crystals of spinel-type LiCoMnO4 were synthesized by heating a mixture of LiOHH2O, CoCl2, and MnCl2 with a molar ratio of Li:Co:Mn = 1.5:1:1 at 750°C. X-ray diffraction (XRD) pattern and scanning electron microscopic (SEM) image showed that LiCoMnO4 has cubic spinel structure with well-formed octahedral crystal shapes. The size of the obtained LiCoMnO4 single crystal particles was about 13 μm. Rietveld analysis using power XRD data confirmed the cubic spinel-type structure with space group Fd-3m, and the lattice parameter of a = 8.05812(14)Å. The tetrahedral 8a site was occupied by both Li and Co atoms with the occupancy values of Li/Co = 0.958/0.042. Electrochemical measurement exhibited the reversible Li-ion extraction and insertion reactions at high potentials. The discharge profile with the discharge capacity of 107mAhg-1 showed three voltage plateaus at 5.1, 4.9, and 3.9V; the former two corresponded to the redox reaction of Co3+/Co4+ and the latter was to the redox reaction of Mn3+/Mn4+, respectively.