Layered LiNi0.5Co0.5O2 cathode materials grown by soft-chemistry via various solution methods

The lithiated nickel–cobalt oxide LiNi0.5Co0.5O2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi0.5Co0.5O2 products calcined at 400–600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi0.5Co0.5O2 compounds. Thermal (TG–DTA) analyses and XRD data show that powders grown with a layered structure (R3 m space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO4 in propylene carbonate, PC). The LiNi0.5Co0.5O2 positive electrodes fired at 600°C exhibited good cycling behavior. © 2000 Elsevier Science S.A. All rights reserved.