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Electronic structure and bonding in energy storage materials.

作者:Shu Miao,
畢業學校:California Institute of Technology
出版單位:California Institute of Technology
核准日期:2007-01-30
類型:Electronic Thesis or Dissertation
權限:unrestricted.I hereby certify that, if appropriate, I have obtained a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, ....

英文摘要

LixNi0.5Mn0.5O2 and LixNi1/3Mn1/3Co1/3O2 are cathode materials in Li-ion batteries. The changes in their electronic structure during charging/discharging processes were studied by using electron energy loss spectrometry (EELS) in a transmission electron microscope (TEM) and first-principles calculations. Significant growth was observed at O K-edge upon the removal of lithium, indicating a depletion of O 2p electrons. Only small changes were observed on Ni absorption edges. Our results indicate that the widely believed Ni2+ -> Ni4+ oxidation does not occur during delithiation, and O is mainly responsible for the charge compensation in these materials. Following similar procedure, the olivine phases of LixFePO4 were studied. It was found that about half electron was donated by Fe atoms during delithiation, while the rest of the charge was contributed by O atoms. We also studied the bonding in Mg2Si. The Mg-Si bond was found to be very ionic. An ionicity of 74% was found via Bader analysis.


committee_member - Marc William Bockrath

committee_member - Rachid Yazami

committee_member - Harry A. Atwater

committee_member - Sossina M. Haile

chair - Brent Fultz


 

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