A series of Co-doped LiMn2O4 spinels of general formula LiCoyMn2-yO4 (0 less than or equal to y less than or equal to 0.66) has been synthesized by a new procedure, i.e. by reacting CoxMn3-xO4 (0 less than or equal to x less than or equal to 0.99) precursors with LiOH . H2O at 600 degrees 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) Angstrom for the LiMn2O4 to 8.0664(4) Angstrom for LiCo0.66Mn1.34O4. The LiCoyMn2-yO4 compounds have small crystallite size, that ranges from 250 to 400 Angstrom. 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. (C) 2000 Elsevier Science B.V. All rights reserved.