Type

Journal Article

Authors

Justin D. Holmes
Colm O'Regan
Arunkumar Panneerselvam
Michael Morris
Mark J. Armstrong

Subjects

Chemistry

Topics
synthesis chemistry organometallic precursors ions capacity fading active material phase amorphous carbon materials cyclic behaviour electrochemical conversion crystallinities crystalline materials lithium supercritical fluids organometallics discharge charge cycle electron transport conversion effluent treatment behaviour powders fluid

Supercritical-fluid synthesis of FeF2 and CoF2 Li-ion conversion materials (2013)

Abstract The synthesis of the Li-ion conversion candidates, FeF2 and CoF2, obtained from the single source organometallic precursors [Fe(tta)3] (tta = C8H4F3O2S), and [Co(hfac)2·2H2O] (hfac = C5H1F6O2), respectively, via a novel supercritical fluid (SCF) method is presented. The nature of the synthesis led to highly-crystalline FeF2 and CoF2 powders requiring no additional thermal treatment. The as-obtained powders were investigated for use as potential positive Li-ion conversion electrodes by means of chronopotentiometric measurements. The FeF2 cells displayed high initial capacities following electrochemical conversion (up to [similar]1100 mA h g−1 at a potential of 1.0 V vs. Li/Li+), with appreciable cyclic behaviour over 25 discharge–charge cycles. The deposition of a [similar]5 nm layer of amorphous carbon onto the surface of the active material following SCF treatment, likely facilitated adequate electron transport through an otherwise poorly conducting FeF2 phase. Similarly, CoF2 cells displayed high initial capacities (up to [similar]650 mA h g−1 at a potential of 1.2 V vs. Li/Li+), although significant capacity fading ensued in the subsequent cycles. Ex situ XRD measurements confirmed a poor reversibility in the conversion sequence for CoF2, with a complete loss of CoF2 crystallinity and the sole presence of a crystalline LiF phase following charging.
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Full list of authors on original publication

Justin D. Holmes, Colm O'Regan, Arunkumar Panneerselvam, Michael Morris, Mark J. Armstrong

Experts in our system

1
Justin D. Holmes
University College Cork
Total Publications: 287
 
2
Colm O'Regan
University College Cork
Total Publications: 16
 
3
Michael A. Morris
University College Cork
Total Publications: 164
 
4
Mark J. Armstrong
University College Cork
Total Publications: 6