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 4V 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 4V 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.