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Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O2
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
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2010 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 157, no 8, A962-A966 p.Article in journal (Refereed) Published
Abstract [en]

We present a study of the charge-state behavior of the Li-ion battery cathode material LixNi(0.65)Co(0.25)Mn(0.1)O(2) as observed by X-ray absorption spectroscopy (XAS) and resonant soft X-ray emission (RSXE). A set of six identical Li//LixNi0.65Co0.25Mn0.1O2 batteries has been cycled and is studied in different states of charge in the range of x = 1.0, ... ,0.2 before disassembly in an Ar glove box. Site and symmetry selective information about the electronic structure of the conduction and valence bands reveals that Ni as well as Co ions participate in the uptake and release of the extra electron charge that the inserted Li ions provide, but the Ni ion is much less than expected. The net amount of charge on the oxygen varies approximately 0.24 charge units in the range of x, and dramatic changes in the hybridization are evident in XAS and in particular in RSXE at the O K edge. We attribute this to a strong screening behavior of the Li ions between the oxide layers. Structural integrity effects limit the extraction of Li ions to a value of about x = 0.2-0.4. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3454739] All rights reserved.

Place, publisher, year, edition, pages
2010. Vol. 157, no 8, A962-A966 p.
National Category
Chemical Sciences Physical Sciences Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
URN: urn:nbn:se:uu:diva-135808DOI: 10.1149/1.3454739ISI: 000279673400010OAI: oai:DiVA.org:uu-135808DiVA: diva2:375918
Available from: 2010-12-09 Created: 2010-12-08 Last updated: 2011-05-05Bibliographically approved
In thesis
1. Redox Reactions in Li-ion Battery Cycling and in Cu Corrosion Studied by Soft X-ray Spectroscopy
Open this publication in new window or tab >>Redox Reactions in Li-ion Battery Cycling and in Cu Corrosion Studied by Soft X-ray Spectroscopy
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The topic of this thesis is redox reactions in two technologically important contexts: firstly, in Li-ion battery electrodes during cycling, and secondly, in copper corrosion in oxygen-free ground water containing sulfide. In an attempt to expand the understanding of the charge uptake process in battery electrodes and the chemical reactions on copper surfaces upon sulfide exposure, soft X-ray spectroscopy has been used to study the electronic structure of these systems.

To ascertain the changes in electron density at different atomic sites in a battery electrode material, both X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) have been applied to different electrode materials. This thesis explains in detail the assembling procedure, cycling, and situ sample preparation of the battery materials. Furthermore, two different designs used in in situ experiments for study of batteries during cycling are also discussed.

The main result from the Li-ion battery materials is the justification to abandon the view of valences as integers. This is true for all battery electrodes examined in this thesis. Generally, oxygen plays a more important role in the charge uptake than commonly assumed, but also the transition metals and other species apart from expected behavior. In LiMnPO4, even the notion of Li as strictly Li+ must be questioned.

Copper is intended to act as a corrosion barrier in a nuclear waste repository. In the corrosion experiments presented in this thesis, different copper oxides were exposed to the conditions present at the planned repository site, with exception for the concentration of sulfide, which was greatly increased.

The conclusion from these experiments is that sulfide effectively reduces Cu(II) oxide to Cu(I) compounds and possibly forms a compound containing both oxygen and sulfur. Also, the thickness and inhomogeneity of the copper oxide surface layers are of great importance for the corrosion mechanisms, including passivation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 69 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 812
National Category
Physical Sciences
urn:nbn:se:uu:diva-148396 (URN)978-91-554-8036-3 (ISBN)
Public defence
2011-05-06, room 2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2011-04-14 Created: 2011-03-05 Last updated: 2011-05-05Bibliographically approved

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Hollmark, Håkan M.Dahbi, MohammedGustafsson, TorbjörnEdström, Kristina
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