Single-phase oxides with Li[Mn2-yCoy]O-4 (0 less than or equal to y less than or equal to 1) stoichiometry and cubic spinel structure have been prepared by using the lactate precursor method. The oxides were alternatively quenched or slow cooled from 750 degreesC. X-ray diffraction and EPR spectroscopy show that Co and Mn are disordered over 16d spinel sites for samples obtained by air quenching. Local environment of Mn4+ was assessed by comparison of the observed EPR spectra for Li[Mn2-yCoy]O-4 compositions with the EPR signal from Mn4+ in LiMnCoO4 and the EPR spectrum of LiMn2O4. Thus, a local Co/Mn ordering is found for spinels obtained by slow-cooling. The use of these materials as the cathodic active compound in lithium cells reveals a higher capacity but lower capacity retention in the 3-4 V regions for metal-quenched samples as compared with slow-cooled products.