TY - JOUR
T1 - Local electronic structure of layered LixNi0.5Mn 0.5O2 and LixNi1/3Mn 1/3Co1/3O2
AU - Miao, Shu
AU - Kocher, Michael
AU - Rez, Peter
AU - Fultz, Brent
AU - Ozawa, Yasunori
AU - Yazami, Rachid
AU - Ahn, Channing C.
PY - 2005/12/15
Y1 - 2005/12/15
N2 - Samples of LixNi0.5Mn0.5O2 and LixNi1/3Mn1/3Co1/3O2 were prepared as active materials in electrochemical half-cells and were cycled electrochemically to obtain different values of Li concentration, x. Absorption edges 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 caused by delithiation. The work was supported by electronic structure calculations with the VASP pseudopotential package, the full-potential linear augmented plane wave code WIEN2K, and atomic multiplet calculations that took account of the electronic effects from local octahedral symmetry. A valence change from Ni2+ to Ni4+ 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 not change enough to account for a substantial change of Ni valence. No changes were detectable at the Mn and Co L-edges after delithiation either. Both EELS and the computational efforts showed that most of the charge compensation for Li+ takes place at hybridized O 2p states, not at Ni atoms.
AB - Samples of LixNi0.5Mn0.5O2 and LixNi1/3Mn1/3Co1/3O2 were prepared as active materials in electrochemical half-cells and were cycled electrochemically to obtain different values of Li concentration, x. Absorption edges 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 caused by delithiation. The work was supported by electronic structure calculations with the VASP pseudopotential package, the full-potential linear augmented plane wave code WIEN2K, and atomic multiplet calculations that took account of the electronic effects from local octahedral symmetry. A valence change from Ni2+ to Ni4+ 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 not change enough to account for a substantial change of Ni valence. No changes were detectable at the Mn and Co L-edges after delithiation either. Both EELS and the computational efforts showed that most of the charge compensation for Li+ takes place at hybridized O 2p states, not at Ni atoms.
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U2 - 10.1021/jp0542266
DO - 10.1021/jp0542266
M3 - Article
C2 - 16375321
AN - SCOPUS:30644456573
SN - 1520-6106
VL - 109
SP - 23473
EP - 23479
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 49
ER -