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LiFePO4 Nanocrystallisation

LiFePO4 Nanocrystallisation

Sundarayya Y, Kumaraswamy K.C., Sunandana C. S.


Homogeneous sub-micron sized particles of surface carbon coatedphase pure LiFePO4 are synthesized by a novel non-aqueousoxalate-based sol-gel route. X-ray diffractogram of LiFePO4 revealsnanocrystals with average crystallite size 32(7) nm. The very largeQS (nearly five times greater than that of Fe3+) value observedfrom Mossbauer spectrum is due to high spin configuration of 3delectrons and the asymmetric local environment at Fe site inLiFePO4. A uniform particle size distribution with grain size 100 ?150nm was observed in SEM with few irregular growths. Our syntheticroute successfully overcomes the incidence of Fe3+, effectivelycontrols undesirable particle growth and has the potential forupscaling and application as Li-ion battery cathodes. Progressiveevolution of olivine structure by the interlock of FeO6 octahedraand PO4 tetrahedra with Li concentration is studied by introducinglithium in to LixFePO4 ( 0.0 x 1.0 ). A fairly abrupt phasetransformation from monoclinic Fe3(PO4)2 to orthorhombic LiFePO4shows up for x~0.2 accompanied by structural disorder which getsstabilized at x 0.35. A systematic study of X-ray diffractogramsshows nanocrystal nucleation and growth from an unstable lowsymmetry crystalline phase with considerable disorder.

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