Preparation and Structural Stability of LiNiO2 in Separate Synthesis Methods at Different Temperatures

Abstract

The LiNiO2 has been the most widely used cathode material in commercial lithium ion batteries because of its high discharge capacity, low cost and environmentally acceptable properties. However, it is difficult to obtain stoichiometric LiNiO2 by solid-state reaction method at high temperature in air atmosphere. This is due to the instability of trivalent nickel species and disordering of cationic distribution at lithium sites. In this paper, we have synthesized the LiNiO2 cathode material by sol-gel and solid state reaction methods at different temperatures (between 750 oC and 800 oC) for obtaining the sample in good phase formation. The sol-gel synthesis method is mainly used because the chemical reaction is easy and also it requires only a low reaction temperature. Further it yields a high degree of homogeneity compared to the conventional solid state synthesis. The crystal structure, bonding nature and vibrational features of the compound are investigated. The crystalline powders are characterized for their phase identification using x-ray diffraction analysis (XRD). All the samples synthesized by these two methods possessed the α-NaFeO2 structure of the rhombohedral system (space group, 3 R m ) with no evidence of any impurities. The morphological features of the powders are characterized by field effect scanning electron microscopy (FESEM). The grain sizes of the samples are found to be approximately 1.5-2 μm. The FT-IR spectroscopic data of LiNiO2 reveal the structure of the oxide lattice constituted by LiO6 and NiO6 octahedra. From this study we conclude that the LiNiO2 synthesized by sol-gel method is structurally stable and it can be used as cathode in lithium ion batteries.