Electrochemical characteristics of cobalt-doped LiCoyMn2−yO4 (0≤y≤0.66) spinels synthesized at low temperature from CoxMn3−xO4 precursors

A series of Co-doped LiMn2O4 spinels of general formula LiCoyMn2−yO4 (0≤y≤0.66) has been synthesized by a new procedure, i.e. by reacting CoxMn3−xO4 (0≤x≤0.99) precursors with LiOH·H2O 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 LiMn2O4 to 8.0664(4) Å for LiCo0.66Mn1.34O4. The LiCoyMn2−yO4 compounds have small crystallite size, that ranges from 250 to 400 Å. The first cycle of the Li//LiCoyMn2−yO4 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.