Synthesis and electrochemical characterization of LiMO2 (M = Ni, Ni0.75Co0.25) for rechargeable lithium ion batteries

A particulate sol-gel (PSG) process has been developed for synthesizing LiNiO2 and LiNixCo1-xO2 (x = 0.75) powders, utilizing the reaction of lithium hydroxide with nickel acetate in a water-ethanol solvent system. Thermal analyses of the as-prepared xerogels show a one step weight loss with a single exothermic peak indicating its chemical homogeneity. Infrared and chemical analyses results of the as-prepared xerogels suggest the possible formation of Ni(OH)(OAc). Generation of lithium carbonate as an intermediate product during the initial heat treatment of the precursors and its decomposition during subsequent heat treatment is the main rate determining step responsible for the formation of the desired lithiated metal oxide. The presence of residual lithium carbonate in the synthesized materials may cause loss in the discharge capacity of the materials. The morphology of the residual lithium carbonate has been investigated using electron microscopy, while its effect on the electrochemical properties has been exemplified. (C) 1998 Elsevier Science B.V. All rights reserved.