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

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Insight Into the Electrochemcal Performance of PEDOT-coated Tavorite LiFeSO4F for Li-ion Batteries
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
Show others and affiliations
(English)Manuscript (preprint) (Other academic)
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-262676OAI: oai:DiVA.org:uu-262676DiVA: diva2:855000
Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2015-10-27
In thesis
1. LiFeSO4F as a Cathode Material for Lithium-Ion Batteries: Synthesis, Structure, and Function
Open this publication in new window or tab >>LiFeSO4F as a Cathode Material for Lithium-Ion Batteries: Synthesis, Structure, and Function
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, two recently discovered polymorphs of LiFeSO4F, adopting a tavorite- and triplite-type structure, were investigated as potential candidates for use as cathode materials in Li-ion batteries. The studies aimed at enriching the fundamental understanding of the synthetic preparations, structural properties, and electrochemical functionality of these materials.

By in situ synchrotron X-ray diffraction (XRD), the formation mechanism of the tavorite-type LiFeSO4F was followed starting from two different sets of precursors, FeSO4∙H2O + LiF, and Li2SO4 + FeF2. The results indicated that the formation of LiFeSO4F is possible only through the structurally related FeSO4∙H2O, in line with the generally recognized topotactic reaction mechanism. Moreover, an in-house solvothermal preparation of this polymorph was optimized with the combined use of XRD and Mössbauer spectroscopy (MS) to render phase pure and well-ordered samples. Additionally, the triplite-type LiFeSO4F was prepared using a facile high-energy ball milling procedure.

The electrochemical performance of as-prepared tavorite LiFeSO4F was found to be severely restricted due to residual traces of the reaction medium (tetraethylene glycol (TEG)) on the surface of the synthesized particles. A significantly enhanced performance could be achieved by removing the TEG residues by thorough washing, and a subsequent application of an electronically conducting surface coating of p-doped PEDOT. The conducting polymer layer assisted the formation of a percolating network for efficient electron transport throughout the electrode, resulting in optimal redox behavior with low polarization and high capacity. In the preparation of cast electrodes suitable for use in commercial cells, reducing the electrode porosity was found to be a key parameter to obtain high-quality electrochemical performance. The triplite-type LiFeSO4F showed similar improvements upon PEDOT coating as the tavorite-type polymorph, but with lower capacity and less stable long-term cycling due to intrinsically sluggish kinetics and unfavorable particle morphology.

Finally, the Li+-insertion/extraction process in tavorite LiFeSO4F was investigated. By thorough ex situ characterization of chemically and electrochemically prepared LixFeSO4F compositions (0≤x≤1), the formation of an intermediate phase, Li1/2FeSO4F, was identified for the first time. These findings helped redefine the (de)lithiation mechanism which occurs through two subsequent biphasic reactions, in contrast to a previously established single biphasic process.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 79 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1291
Keyword
Li-ion battery, cathode, LiFeSO4F, tavorite, triplite, synthesis, performance, structure, coating, PEDOT, XRD, Mössbauer spectrocopy, SEM, TEM, electrochemistry
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-262715 (URN)978-91-554-9344-8 (ISBN)
Public defence
2015-11-05, Häggsalen, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-10-14 Created: 2015-09-18 Last updated: 2015-10-27

Open Access in DiVA

No full text

By organisation
Department of Chemistry - Ångström
Materials Chemistry

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 420 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf