Structural, Magnetic and Electrochemical Properties of the Spinel LiMn_2-yCo_yO₄ Nanosized Powders

Abstract

We present the synthesis, structure, magnetic properties and electrode behaviour of LiMn_2-yCo_yO₄ (0≤y≤0) spinel oxides prepared by the wet-chemitry via the carboxylic acid route. LiMn_2-yCo_yO₄ samples crystallise with the cubic spinel-like structure (Fd3m S.G.). Optical spectra indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Co,Mn)-O bonds. Magnetic susceptibility and electron spin resonance measurements show the compositional dependence of the magnetic parameters, i.e. Curie temperature, Curie-Weiss constant and Néel temperature, when Mn is substituted by Co. The overall electrochemical capacity of LiMn_2-yCo_yO₄ oxides have been reduced due to the 3d⁶ metal substitution, however, a more stable charge-discharge cycling performances have been observed when electrodes are charged up to 4.3 V as compared to the performance of the native oxide.