Electrochemical characteristics of cobalt-doped LiCo yMn 2− yO 4 (0≤ y≤0.66) spinels synthesized at low temperature from Co xMn 3− xO 4 precursors

Abstract

A series of Co-doped LiMn 2O 4 spinels of general formula LiCo y Mn 2− y O 4 (0≤ y≤0.66) has been synthesized by a new procedure, i.e. by reacting Co x Mn 3− x O 4 (0≤ x≤0.99) precursors with LiOH·H 2O at 600°C for 4 h. Structural and electrochemical characterization has been carried out. The spinels have been obtained as single-phase compounds, with lattice parameters decreasing from 8.2090(4) Å for the LiMn 2O 4 to 8.0664(4) Å for LiCo 0.66Mn 1.34O 4. The LiCo y Mn 2− y O 4 compounds have small crystallite size, that ranges from 250 to 400 Å. The first cycle of the Li//LiCo y Mn 2− y O 4 cells has been studied by step potential electrochemical spectroscopy (SPECS). The lithium extraction/insertion mechanism has been studied. A linear diminution of the spinel capacity on increasing the Co-dopant content is observed for the first cycle. For the doped spinels a remarkable enhancement of the cyclability with a retention of the initial capacity >90% after 12 cycles at low current density (C/30) is observed.