Electronic Structure of Chemically-Delithiated LiCoO_2 Studied by Electron Energy-Loss Spectrometry

The electronic structure of chemically delithiated Li_(1-x)CoO_2 (x = −0.02, 0.09, 0.12, 0.20, and 0.28) was investigated by electron energy-loss spectrometry (EELS). The O K edge and Co L_(2,3) edge were used to probe the density of unoccupied states around the O and Co ions at different states of lithiation. The O ions accommodate the incoming charge during Li intercalation. The net electron density surrounding the Co ions is less affected. This is in substantial agreement with prior electronic structure calculations of Van der Ven, et al., whose atomic structure data were used in the present calculations of EELS cross-sections. Calculations of the O 2p partial densities of state curves confirm the increase in unoccupied states that accompany Li extraction.