uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Improved performances of nanosilicon electrodes using the salt LiFSI: A photoelectron spectroscopy study
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
Show others and affiliations
2013 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 26, 9829-9842 p.Article in journal (Refereed) Published
Abstract [en]

Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft X-rays (100–800 eV) and hard X-rays (2000–7000 eV) from two different synchrotron facilities and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2013. Vol. 135, no 26, 9829-9842 p.
National Category
Physical Chemistry
URN: urn:nbn:se:uu:diva-198221DOI: 10.1021/ja403082sISI: 000321541800045OAI: oai:DiVA.org:uu-198221DiVA: diva2:615492
Available from: 2013-04-10 Created: 2013-04-10 Last updated: 2013-09-10Bibliographically approved
In thesis
1. Insights in Li-ion Battery Interfaces through Photoelectron Spectroscopy Depth Profiling
Open this publication in new window or tab >>Insights in Li-ion Battery Interfaces through Photoelectron Spectroscopy Depth Profiling
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Compounds forming alloys with lithium, such as silicon or tin, are promising negative electrode materials for the next generation of Li-ion batteries due to their higher theoretical capacity compared to the current commercial electrode materials.

An important issue is to better understand the phenomena occurring at the electrode/electrolyte interfaces of these new materials. The stability of the passivation layer (SEI) is crucial for good battery performance and its nature, formation and evolution have to be investigated. It is important to follow upon cycling alloying/dealloying processes, the evolution of surface oxides with battery cycling and the change in surface chemistry when storing electrodes in the electrolyte.

The aim of this thesis is to improve the knowledge of these surface reactions through a non-destructive depth-resolved PES (Photoelectron spectroscopy) analysis of the surface of new negative electrodes. A unique combination utilizing hard and soft-ray photoelectron spectroscopy allows by variation of the photon energy an analysis from the extreme surface (soft X-ray) to the bulk (hard X-ray) of the particles. This experimental approach was used to access the interfacial phase transitions at the surface of silicon or tin particles as well as the composition and thickness/covering of the SEI.

Interfacial mechanisms occurring upon the first electrochemical cycle of Si-based electrodes cycled with the classical salt LiPF6 were investigated.

The mechanisms of Li insertion (LixSi formation) have been illustrated as well as the formation of a new irreversible compound, Li4SiO4, at the outermost surface of the particles. Upon long cycling, the formation of SiOxFy was shown at the extreme surface of the particles by reaction of SiO2 with HF contributing to battery capacity fading.

The LiFSI salt, more stable than LiPF6, improved the electrochemical performances. This behaviour is correlated to the absence of SiOxFy upon long-term cycling. Some degradation of LiFSI was shown by PES and supported by calculations.

Finally, interfacial reactions occurring upon the first cycle of an intermetallic compound MnSn2 were studied. Compared to Si based electrodes, the SEI chemical composition is similar but the alloying process and the role played by the surface metal oxide are different.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 200 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1041
Lithium-ion batteries, negative electrodes, silicon, MnSn2, SEI, PES, XPS, synchrotron
National Category
Materials Chemistry Physical Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
urn:nbn:se:uu:diva-197250 (URN)978-91-554-8662-4 (ISBN)
Public defence
2013-05-24, Amphithéâtre de l'IPREM, 2 avenue du Président Pierre Angot, Pau, France, 10:00 (English)
Available from: 2013-05-03 Created: 2013-03-20 Last updated: 2013-08-30Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Philippe, BertrandRensmo, HåkanEdström, Kristina
By organisation
Structural ChemistryMolecular and condensed matter physics
In the same journal
Journal of the American Chemical Society
Physical Chemistry

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 648 hits
ReferencesLink to record
Permanent link

Direct link