Co/Mn distribution and electrochemical intercalation of Li into Li[Mn 2− yCo y]O 4 spinels, 0< y≤1

Abstract

Single-phase oxides with Li[Mn 2− y Co y ]O 4 (0≤ y≤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°C. 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 Mn 4+ was assessed by comparison of the observed EPR spectra for Li[Mn 2− y Co y ]O 4 compositions with the EPR signal from Mn 4+ in LiMnCoO 4 and the EPR spectrum of LiMn 2O 4. 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.