Structural and electrochemical characterization of sulphur-doped lithium manganese spinel cathode materials for lithium ion batteries

Abstract

Nanosized LiMn2O4 and LiMn2O3.99S0.01 powders were prepared using a modified sol-gel method followed by calcination at 300°C and further calcination at 650°C in air. The high-temperature calcination was required to receive improved structural and electrical properties of the spinels. X-ray powder diffraction showed that for samples calcined at 650°C, single phase materials of Fd-3m symmetry with nanoparticles size of ~50nm were obtained. The LiMn2O4 spinel showed the phase transition at about room temperature, but the effect was strongly diminished with the substitution of sulphur for oxygen in the spinel structure. Electrochemical results on 2032 coin-type cells reveal that slight substitution of sulphur in the LiMn2O4 enhances the electrochemical performance and cell cycleability. The sulphided cathode material in which the capacity retention after 50cycles is around 99% displays good rate capability, even at higher current densities.