Capacity fading of high specific capacity spinel LixMn2-yTiyO4 as cathode material for Li-ion batteries

A facile sol-gel method is presented and used to optimize LixMn2-yTiyO4 spinel-type materials for Li-ion battery cathodes while maintaining nanostructured features and minimizing the formation of TiO2 impurities. LiMn1.8Ti0.2O4 exhibited the best initial specific capacity of 215 mA h g(-1) at 30.8 mA g(-1) in a window potential of 4.6 - 2.0 V vs. Li vertical bar Li+. The addition of Ti improved the specific capacity thanks to possibility of using both Mn4+vertical bar Mn3+ and Mn3+vertical bar Mn2+ transitions. However, capacity fading issues persist. The effect of Ti incorporation and degradation processes during cycling were studied by cyclic voltammetry, charge/discharge cycling and EIS, the latter was analyzed by seldom used distribution of relaxations times (DRT) and compared to the results obtained by fitting to equivalent electrical circuits. Cathode materials were characterized by XPS, Raman and BET surface area and at different cycling stages by XRD, Synchrotron XRD and SEM. The results showed undesired structure modifications for the transition Mn3+vertical bar Mn2+ and the formation of irreversible tetragonal phase that increased charge transfer resistances. [GRAPHICS] .