Synthesis and characterization of LiNi 1/3Mn 1/3Co 1/3O 2 by wet-chemical method

Abstract

A series of LiNi 1/3Mn 1/3Co 1/3O 2 samples with α-NaFeO 2 structure belonging to the R 3 ¯ m D 3d 5 space group were synthesized using tartaric acid as a chelating agent by wet-chemical method. Different acid to metal-ion ratios R have been used to investigate the effect of this parameter on the physical and electrochemical properties. We have characterized the reaction mechanism, the structure, and morphology of the powders by TGA, XRD, SEM and TEM imaging, completed by magnetic measurements, Raman scattering spectroscopy, and complex impedance experiments. We find that the LiNi 1/3Mn 1/3Co 1/3O 2 sintered at 900 °C for 15 h with an acid to metal-ion ratio R = 2 was the optimum condition for this synthesis. For this optimized sample, only 1.3% of nickel-ions occupied the 3 b Wyckoff site of the lithium-ions sublattice. The electrochemical performance has been investigated using a coin-type cell containing Li metal as the anode. The electronic performance is correlated to the concentration of the Ni(3 b) defects that increase the charge transfer resistance and reduce the lithium diffusion coefficient. The optimized cell delivered an initial discharge capacity of 172 mAh g −1 in the cut-off voltage of 2.8–4.4 V, with a coulombic efficiency of 93.4%.