Co/Mn distribution and electrochemical intercalation of Li into Li[Mn2-yCoy]O-4 spinels, 0 < y <= 1

Single-phase oxides with Li[Mn2-yCoy]O-4 (0 less than or equal to y less th an or equal to 1) stoichiometry and cubic spinel structure have been prepar ed by using the lactate precursor method. The oxides were alternatively que nched or slow cooled from 750 degreesC. X-ray diffraction and EPR spectrosc opy show that Co and Mn are disordered over 16d spinel sites for samples ob tained by air quenching. Local environment of Mn4+ was assessed by comparis on of the observed EPR spectra for Li[Mn2-yCoy]O-4 compositions with the EP R signal from Mn4+ in LiMnCoO4 and the EPR spectrum of LiMn2O4. Thus, a loc al 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 meta l-quenched samples as compared with slow-cooled products. (C) 2001 Elsevier Science B,V. All rights reserved.