Change search
ReferencesLink to record
Permanent link

Direct link
Redox Reactions in Li-ion Battery Cycling and in Cu Corrosion Studied by Soft X-ray Spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. (Mjukröntgenfysik, Soft X-Ray Physics)
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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 812
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-148396ISBN: 978-91-554-8036-3OAI: oai:DiVA.org:uu-148396DiVA: diva2:405881
Public defence
2011-05-06, room 2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2011-04-14 Created: 2011-03-05 Last updated: 2011-05-05Bibliographically approved
List of papers
1. Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O2
Open this publication in new window or tab >>Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O2
Show others...
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.

National Category
Chemical Sciences Physical Sciences Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-135808 (URN)10.1149/1.3454739 (DOI)000279673400010 ()
Available from: 2010-12-09 Created: 2010-12-08 Last updated: 2011-05-05Bibliographically approved
2. Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the negative electrode material Li0.5Ni0.25TiOPO4 in a Li-ion battery
Open this publication in new window or tab >>Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the negative electrode material Li0.5Ni0.25TiOPO4 in a Li-ion battery
Show others...
2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 14, 6544-6551 p.Article in journal (Refereed) Published
Abstract [en]

We have studied the first lithiation/delithiation cycle of the Li-ion battery electrode material LixNi0.25TiOPO4 applying X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). A set of ten identical LixNi0.25TiOPO4 battery electrodes have been cycled and left in different states of charge in the range of x = 0.5 … 2.5, before disassembly in an Ar filled glove box. We find that Ni-, Ti-, and O-ions are affected simultaneously, rather than sequentially, upon lithiation of the material. In particular, Ni is reduced from Ni2+ to Ni0 but only partially re-oxidized to Ni1+, again, by delithiation. Overall, there is considerable “crosstalk” between the different atomic species and non-linearity in the response of the electronic structure during the lithiation/delithiation process. Fortuitously, the background variation in Ni L-XAS shows to contain valuable information about solid–electrolyte interface (SEI) creation, showing that the SEI is a function of the degree of lithiation.

Keyword
Valence number, Soft X-ray spectroscopy, Li-ion battery, RIXS
National Category
Atom and Molecular Physics and Optics Inorganic Chemistry
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics; Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-149316 (URN)10.1039/C0CP02668A (DOI)000288678900017 ()
Available from: 2011-03-17 Created: 2011-03-17 Last updated: 2011-11-29Bibliographically approved
3. Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the cathode materials LiMnPO4 and LiMn0.9Fe0.1PO4: A comparative study
Open this publication in new window or tab >>Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the cathode materials LiMnPO4 and LiMn0.9Fe0.1PO4: A comparative study
2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 45, 20215-20222 p.Article in journal (Refereed) Published
Abstract [en]

We present a study of the charge-state behavior of the Li-ion battery cathode materials LixMnPO4 and LixMn0.9Fe0.1PO4 usingx-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). A set of six identical battery cathodesfor each material have been cycled and left in different charge states in the range of x=0.2...1.0 before disassembly in an Arglove box. Unexpectedly, we find that the Mn 3d-bands are almost inert to the delithiation process, suggesting that Mn ionsparticipate to a very small extent in the charge compensation process. In LixMn0.9Fe0.1PO4 the Fe 3d-band shows much moreresponse to delithiation than the Mn 3d-band. The O 2p-band hybridizes with the bands of the other ions in LixMnPO4 and LixMn0.9Fe0.1PO4 and thus, indirectly, carries useful information about the effects of delithiation at all ion sites. We conclude,that the redox reactions during lithiation/delithiation of these materials are complex and involve repopulation of charges for allconstituent elements.

Place, publisher, year, edition, pages
Cambridge, UK: RCS Publishing, 2011
Keyword
Valence number, X-ray spectroscopy, Li-ion battery, RIXS
National Category
Atom and Molecular Physics and Optics Inorganic Chemistry
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics; Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-149320 (URN)10.1039/c1cp20673g (DOI)000296871500024 ()
Available from: 2011-03-17 Created: 2011-03-17 Last updated: 2011-12-13Bibliographically approved
4. Exposure of Oxidized Copper Surfaces to Aqueous Na2S Solution Studied with Soft X-Ray Spectroscopy
Open this publication in new window or tab >>Exposure of Oxidized Copper Surfaces to Aqueous Na2S Solution Studied with Soft X-Ray Spectroscopy
Show others...
2011 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 158, no 1, C1-C5 p.Article in journal (Refereed) Published
Abstract [en]

We present results from X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) of oxidized polycrystalline copper surfaces [Cu(I) and Cu(II), respectively] exposed to a 1.0 mM aqueous solution of Na2S (sodium sulfide) for several hours. Scanning electron microscopy reveals that the Cu oxide surfaces attain a much rougher texture upon sodium sulfide exposure, and that the exposed Cu(II) oxide sample exhibits areas with crystallites. The XAS spectra show that sodium sulfide effectively reduces Cu(II) oxide to Cu(I) compounds. The RIXS spectra of the exposed surfaces closely resemble those of the Cu2O reference sample with the notable exception of their Cu LIII,II-RIXS spectra. We conclude that copper evidently forms a Cu(I) compound with oxygen but with a Cu 3d-band of much reduced width, pointing to the possibility of a more complex compound containing both oxygen and sulfur.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-139392 (URN)10.1149/1.3504891 (DOI)000284697900020 ()
Available from: 2010-12-27 Created: 2010-12-23 Last updated: 2013-10-16Bibliographically approved
5. X-ray absorption spectroscopy on electrochemically oxidized Cu exposed toNa2S
Open this publication in new window or tab >>X-ray absorption spectroscopy on electrochemically oxidized Cu exposed toNa2S
Show others...
2011 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 54, 85-89 p.Article in journal (Refereed) Published
Abstract [en]

Copper surfaces have been investigated by X-ray absorption spectroscopy after electrochemical oxidation and subsequent exposure to sulfide solution. Oxide surface layers on bulk copper surfaces were electrochemically grown in anaqueous NaOH solution at two different potentials and the resulting chemical composition was investigated using X-ray absorption spectroscopy. At both potentials the resulting surfaces consisted largely of Cu2O. At the more strongly oxidizing potential, an admixture of Cu2+-containing phases – mostly Cu(OH)2 – was detected. Sulfide exposure of both surfaces was found to completely reduce the surface from Cu2+ to Cu1+ and resulted in the formation of Cu2S with an admixture of Cu2O.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2011
National Category
Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-149328 (URN)10.1016/j.corsci.2011.09.001 (DOI)000297894000012 ()
Available from: 2011-03-17 Created: 2011-03-17 Last updated: 2012-01-13Bibliographically approved

Open Access in DiVA

fulltext(6403 kB)1979 downloads
File information
File name FULLTEXT01.pdfFile size 6403 kBChecksum SHA-512
cfd5f10ba49877ee5a6dd1815b0146bd9fc1edb949b014e9880b22f7df731015d9f5bfbf7bac0fbd3e6c1638fd83c5fca685c1cc7803e49a5ce5a0c9a8bdb9cf
Type fulltextMimetype application/pdf
Buy this publication >>

Search in DiVA

By author/editor
Hollmark, Håkan
By organisation
Department of Physics and Astronomy
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 1979 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 726 hits
ReferencesLink to record
Permanent link

Direct link