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Study of the Li-insertion / extraction process in LiFePO4/FePO4

Abstract : The structural properties of LiFePO4 prepared by the hydrothermal route and chemically delithiated have been studied using analytical electron microscopy and Raman spectroscopy. High-resolution transmission electron microscopy and selected area electron diffraction measurements indicate that the partially delithiated particles include LiFePO4 regions with cross-sections of finite size along the ac-plane, as a result of tilt grain boundary in the bc-plane, and dislocations in other directions. Only the boundary along the bc-plane is accompanied by a disorder over about 2 nm on each side of the boundary. The Raman spectrum shows the existence of both LiFePO4 and FePO4 phases in the shell of the particles at a delithiation degree of 50%, which invalidates the core–shell model. This result also invalidates the recent model according to which each particle would be single-domain, i.e. either a LiFePO4 particle or a FePO4 particle. On the other hand, our results, like prior ones, can be understood within the framework of a model similar to the spinodal decomposition of a two-phase system, which is discussed within the framework of morphogenesis of patterns in systems at equilibrium. Both end-members, however, are well crystallized, suggesting a recovery similar to that observed in superplastic alloys, with dynamics that are due to the motion of nucleation fronts and dislocations, and not due to a diffusion phenomenon associated with a concentration gradient.
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https://hal.archives-ouvertes.fr/hal-00357449
Contributor : Danielle Thomas Connect in order to contact the contributor
Submitted on : Friday, January 30, 2009 - 2:03:35 PM
Last modification on : Saturday, January 15, 2022 - 3:44:36 AM

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C.V. Ramana, A. Mauger, F. Gendron, C.M. Julien, K. Zaghib. Study of the Li-insertion / extraction process in LiFePO4/FePO4. Journal of Power Sources, Elsevier, 2009, 187, pp.555. ⟨10.1016/j.jpowsour.2008.11.042⟩. ⟨hal-00357449⟩

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