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Electrochemical performances and mechanisms of MnSn2 as anode material for Li-ion batteries
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2013 (English)In: Journal of Power Sources, ISSN 0378-7753, Vol. 244, 246-251 p.Article in journal (Refereed) Published
Abstract [en]

A synthesis method consisting of a mechanical ball milling activation process followed by a sinteringheating treatment is proposed to obtain MnSn2 as anode material for Li-ion batteries. This two-stepapproach strongly reduces the amount of bSn impurities and provides a better material morphology.This improves the electrochemical performances, even at high C-rate, as shown from the comparisonbetween electrode materials obtained with and without this preliminary activation process. The electrochemicalreactions have been followed at the atomic scale by in situ 119Sn Mössbauer spectroscopy.The first discharge is a restructuring step that transforms the pristine material into Mn/Li7Sn2 nanocompositewhich should be considered as the real starting material for cycling. The delithiation of thisnanocomposite is characterized by two plateaus of potential attributed to the de-alloying of Li7Sn2 followedby the back reaction of Mn with poorly lithiated LixSn alloys, respectively. The composition and thestability of the solid electrolyte interphase were characterized by X-ray photoelectron spectroscopy.

Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 244, 246-251 p.
National Category
Inorganic Chemistry
URN: urn:nbn:se:uu:diva-197842DOI: 10.1016/j.jpowsour.2013.01.110OAI: oai:DiVA.org:uu-197842DiVA: diva2:614498
16th International Meeting on Lithium Batteries (IMLB)
Available from: 2013-04-04 Created: 2013-04-04 Last updated: 2014-09-11Bibliographically 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

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