Synthesis and electrode properties of nanocrystalline lithium copper iron oxide cathodes

Lithium copper iron oxides (LixCu1-yFeyOz) have been synthesized by a solution-based procedure involving the oxidation of a mixture consisting of Fe2+ and Cu2+ ions with the oxidizing agent Li2O2 in presence of LiOH.H2O. The samples before and after heat-treatment at various temperatures (200-800degreesC) have been characterized by X-ray diffraction, transmission electron microscopy (TEM), and atomic absorption spectroscopy. The composition of the product LixCu1-yFeyOz is controlled by the concentration of the reactants. TEM data reveal the 200degreesC samples to be nanocrystalline although X-ray diffraction does not show any discernible reflections. The 200-300degreesC heated samples show high initial capacity of around 300 mAh/g in the voltage range of 1.5 to 4.3 V. With optimized compositions, a reversible capacity of around 230 mAh/g could be achieved with good cyclability. (C) 2002 The Electrochemical Society.