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Title: X-ray absorption spectroscopic study of chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds

Abstract

The local structure refinements for chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds have been investigated by Co K-edge X-ray absorption spectroscopy. In the X-ray absorption near-edge structure (XANES), the 1s {r_arrow} 3d transition at {approximately} 7,709.9 eV and 1s {r_arrow} 4p transition at {approximately} 7,727.8 eV for the pristine LiCo{sub 0.85}Al{sub 0.15}O{sub 2} have shifted effectively to higher energy regions of {approximately} 0.6 eV and {approximately} 2.5 eV for the higher Li ion extraction, respectively, which shows that the average oxidation state of Co ion increases gradually with the extraction. The systematic variations of peak intensities for the 1s {r_arrow} 3d transition and 1s {r_arrow} 4p transition result from Co 3d and 4p orbital mixing by the local structure distortion around Co atoms. In particular, the abrupt decrease of peak intensity for 1s {r_arrow} 4p transition with shakedown process by ligand to metal charge transfer (LMCT) represents the transfer of the hole state from the oxygen to Co atom and the localization at the Co atomic site as a form of Co{sup IV} ion by structural distortion. The XANES features for the electrochemical extraction have shown that the electrochemical redox reaction is always not reversiblemore » in the Li ion extraction/insertion process. From the extended X-ray absorption fine structure (EXAFS) refinement, the interatomic distances of bond pairs decrease for the Li ion extraction. The chemical and electrochemical extractions have a significant effect on Fourier transform (FT) magnitude, which decreases linearly with the extraction. Since single and multiple scatterings with Co atoms have predominantly contributed to the FT magnitudes, the systematic decrease of FT magnitude is closely related to the static disorder of two different oxidative Co{sup III} and Co{sup IV} ions. This fact is consistent with the increase of the Debye-Waller factor for each bond pair.« less

Authors:
;  [1]
  1. Yonsei Univ., Seoul (Korea, Republic of). Dept. of Chemistry
Publication Date:
OSTI Identifier:
682066
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 103; Journal Issue: 31; Other Information: PBD: 5 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 36 MATERIALS SCIENCE; LITHIUM; X-RAY SPECTROSCOPY; LITHIUM COMPOUNDS; COBALT COMPOUNDS; LIGANDS; ELECTRONIC STRUCTURE

Citation Formats

Kim, M.G., and Yo, C.H. X-ray absorption spectroscopic study of chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds. United States: N. p., 1999. Web. doi:10.1021/jp990753b.
Kim, M.G., & Yo, C.H. X-ray absorption spectroscopic study of chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds. United States. doi:10.1021/jp990753b.
Kim, M.G., and Yo, C.H. Thu . "X-ray absorption spectroscopic study of chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds". United States. doi:10.1021/jp990753b.
@article{osti_682066,
title = {X-ray absorption spectroscopic study of chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds},
author = {Kim, M.G. and Yo, C.H.},
abstractNote = {The local structure refinements for chemically and electrochemically Li ion extracted Li{sub y}Co{sub 0.85}Al{sub 0.15}O{sub 2} compounds have been investigated by Co K-edge X-ray absorption spectroscopy. In the X-ray absorption near-edge structure (XANES), the 1s {r_arrow} 3d transition at {approximately} 7,709.9 eV and 1s {r_arrow} 4p transition at {approximately} 7,727.8 eV for the pristine LiCo{sub 0.85}Al{sub 0.15}O{sub 2} have shifted effectively to higher energy regions of {approximately} 0.6 eV and {approximately} 2.5 eV for the higher Li ion extraction, respectively, which shows that the average oxidation state of Co ion increases gradually with the extraction. The systematic variations of peak intensities for the 1s {r_arrow} 3d transition and 1s {r_arrow} 4p transition result from Co 3d and 4p orbital mixing by the local structure distortion around Co atoms. In particular, the abrupt decrease of peak intensity for 1s {r_arrow} 4p transition with shakedown process by ligand to metal charge transfer (LMCT) represents the transfer of the hole state from the oxygen to Co atom and the localization at the Co atomic site as a form of Co{sup IV} ion by structural distortion. The XANES features for the electrochemical extraction have shown that the electrochemical redox reaction is always not reversible in the Li ion extraction/insertion process. From the extended X-ray absorption fine structure (EXAFS) refinement, the interatomic distances of bond pairs decrease for the Li ion extraction. The chemical and electrochemical extractions have a significant effect on Fourier transform (FT) magnitude, which decreases linearly with the extraction. Since single and multiple scatterings with Co atoms have predominantly contributed to the FT magnitudes, the systematic decrease of FT magnitude is closely related to the static disorder of two different oxidative Co{sup III} and Co{sup IV} ions. This fact is consistent with the increase of the Debye-Waller factor for each bond pair.},
doi = {10.1021/jp990753b},
journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
number = 31,
volume = 103,
place = {United States},
year = {1999},
month = {8}
}