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A neutron powder diffraction study of LiCoxFe1−xPO4 for x = 0, 0.25, 0.40, 0.60 and 0.75
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
2006 (English)In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, no 15-16, 1327-1330 p.Article in journal (Refereed) Published
Abstract [en]

X-ray and neutron powder diffraction studies have been made of the single-phase systems LiCoxFe1−xPO4 (x = 0, 0.25, 0.40, 0.60 and 0.75) to establish how Co2+ substitutes into the LiFePO4 olivine structure. Rietveld refinement shows that all four substituted materials have the same olivine structure (space group: Pnma) with lithium occupying octahedral (4a) sites, and Co2+ replacing Fe2+ at the octahedral (4c) sites. The a and b cell parameters decrease while the c parameter increases on the addition of Co2+. There are certain indications of structural instability for high Co-content compositions.

Place, publisher, year, edition, pages
2006. Vol. 177, no 15-16, 1327-1330 p.
Keyword [en]
Lithium iron phosphate, Cobalt substitution, Neutron diffraction
National Category
Inorganic Chemistry
URN: urn:nbn:se:uu:diva-82129DOI: 10.1016/j.ssi.2006.05.019ISI: 000241351900013OAI: oai:DiVA.org:uu-82129DiVA: diva2:110044
Available from: 2006-09-19 Created: 2006-09-19 Last updated: 2013-05-17Bibliographically approved
In thesis
1. Low-Cost Iron-Based Cathode Materials for Large-Scale Battery Applications
Open this publication in new window or tab >>Low-Cost Iron-Based Cathode Materials for Large-Scale Battery Applications
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O2-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO4. A second and in some ways even more attractive material - Li2FeSiO4 - has emerged during the course of this work.

An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li2FeSiO4. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li2FeSiO4 and LiFeSiO4, but with the structure of the original Li2FeSiO4 transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li2FeSiO4 and the delithiated on LiFeSiO4 structure provide an interesting insight into the experimental result.

Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO4 and Li2FeSiO4 after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling.

LiFePO4 and Li2FeSiO4 should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 54 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 179
Inorganic chemistry, Li-ion battery, cathode material, lithium iron phosphate, lithium iron silicate, X-ray powder diffraction, Mössbauer spectroscopy, photoelectron spectroscopy, Oorganisk kemi
urn:nbn:se:uu:diva-6842 (URN)91-554-6559-5 (ISBN)
Public defence
2006-05-12, Häggsalen, The Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15
Available from: 2006-04-21 Created: 2006-04-21 Last updated: 2013-05-17Bibliographically approved

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