Structure transformation of LiAl0.15Mn1.85O4 cathode material during charging and discharging in aqueous solution

The electrochemical lithium-ion extraction/insertion properties of a spinel LiAl0.15Mn1.85O4 material were studied. Cyclic voltammetry shows two-step reactions for lithium-ion extraction/insertion at its 4 V plateau. Synchrotron in situ X-ray diffraction studies show that lithium ions are extracted and inserted from the LiAl0.15Mn1.85O4 material, respectively, from two to three different environments. The different environments may be due to different Li-Li interactions and/or different intensities of interactions with the nearest neighbors in the spinel LiAl0.15Mn1.85O4 material frame work. From the Mn absorption edge measurements as a function of potential, during lithium extraction, it can be suggested that the charge transfer rate is faster than that of structural transformations. However, during lithium insertion, the rate of both charge transfer and structural transformations are more or less similar. (C) 2003 Published by Elsevier Science B.V.