Evolution of local electronic and atomic structure of Co-doped LiMn2O4 cathode material for lithium rechargeable batteries

In situ X-ray absorption spectroscopy (XAS) techniques are performed to investigate the evolution of the local electronic and atomic structure of a spinel cathode material LiCO0.2Mn1.8O4 in the 4 V range. Changes in the oxidation state, bond distance, and local disorder of Mn and Co absorbers in the Co-doped LiMn2O4 are measured as a function of potentials. The X-ray absorption near edge spectra shows that charging (Li deintercalation) leads to the oxidation of manganese to Mn4+. On the other hand, Co atoms are also oxidized but the edge energy shift is small, which suggests that Co is also electroactive in LiCo0.2Mn1.8O4 in the 4 V range. The change in the Debye-Waller factor of the Co-O shell is smaller than that of Mn-O shell. Furthermore, from Debye-Waller factor and bond distance values, it appears that the Co environment fluctuates markedly during discharging. (C) 2003 Elsevier Science B.V. All rights reserved.