| Abstract
| - Samples of LixNi0.5Mn0.5O2 and LixNi1/3Mn1/3Co1/3O2 were prepared as active materials in electrochemicalhalf-cells and were cycled electrochemically to obtain different values of Li concentration, x. Absorptionedges of Ni, Mn, Co, and O in these materials of differing x were measured by electron energy loss spectrometry(EELS) in a transmission electron microscope to determine the changes in local electronic structure causedby delithiation. The work was supported by electronic structure calculations with the VASP pseudopotentialpackage, the full-potential linear augmented plane wave code WIEN2K, and atomic multiplet calculationsthat took account of the electronic effects from local octahedral symmetry. A valence change from Ni2+ toNi4+ with delithiation would have caused a 3 eV shift in energy of the intense white line at the Ni L3 edge,but the measured shift was less than 1.2 eV. The intensities of the “white lines” at the Ni L-edges did notchange enough to account for a substantial change of Ni valence. No changes were detectable at the Mn andCo L-edges after delithiation either. Both EELS and the computational efforts showed that most of the chargecompensation for Li+ takes place at hybridized O 2p states, not at Ni atoms.
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