Lithium iron phosphate (LiFePO4) is one of the most promising cathode materials for lithium
ion rechargeable batteries. It has a high theoretical specific capacity (170 mAh/g) and
operating potential (3.45 V vs. Li+/Li). Additionally, the material is extremely stable thermally
and electrochemically at ambient conditions, which is very suitable to be used in electric
vehicles. However, the electronic and ionic conductivities of the material are quite low, which
limits the power performance of the batteries. In the last decade, extensive work was reported
on various methods to improve the electronic conductivity extrinsically, for example carbon
coating, metallic additives and molecular wiring. Nevertheless, energy density of the cells will
be reduced because of non-electrochemically active nature of the additives. In principle,
electronic and ionic conductivities can be boosted intrinsically. One of the methods is to
increase the number of charge carriers in the material, for instance in two-phase
solid solution system LiαFePO4/Li1-βFePO4 or single solid solution phase LixFePO4. Since the
formation of solid solution has been reported to be size dependent, it is highly desired to know
how to synthesize LiFePO4 particles with different sizes. In this study, we have used
hydrothermal synthesis and polyol process to control the size of LiMPO4 (M: Fe, Mn, and Co)
particles. We will present how we prepare particles with different sizes. Moreover, the solid
solution properties of various sizes of LiMPO4 (M: Mn and Fe) were studied. The result will be
presented.
Part of the preliminary findings have been published in the peer-reviewed journals or
conference presentations: 1) Journal of Materials Chemistry [Ellis B.; Kan W. H.; Makahnouk
W. R. M.; Nazar L. F. J. Mater. Chem. 2007, 17 (30) 3248., 2) Journal of the American
iv
Chemical Society [Lee K. T.; Kan W. H.; Nazar L. F. J. Am. Chem. Soc. (submitted)], 3)
Material Research Society Meeting [Kan W. H.; Maunders C.; Badi S.; Ellis B.; Botton G.;
Nazar L. F. MRS Fall Meeting 2008 in Boston]
| Identifer | oai:union.ndltd.org:WATERLOO/oai:uwspace.uwaterloo.ca:10012/4313 |
| Date | January 2009 |
| Creators | Kan, Wang Hay |
| Source Sets | University of Waterloo Electronic Theses Repository |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
Page generated in 0.0019 seconds