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

Abstract

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 LiCo 0.2 Mn 1.8 O 4 in the 4 V range. Changes in the oxidation state, bond distance, and local disorder of Mn and Co absorbers in the Co-doped LiMn 2 O 4 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 Mn 4+ . On the other hand, Co atoms are also oxidized but the edge energy shift is small, which suggests that Co is also electroactive in LiCo 0.2 Mn 1.8 O 4 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.