X-Ray Photoelectron Spectroscopy investigations of carbon-coated Li_xFePO₄ materials

Rémi Dedryvère (1) , Magalie Maccario (2) , Laurence Croguennec (2) , Frédéric Le Cras (3) , Claude Delmas (2) , Danielle Gonbeau (1)

1 IPREM - Institut pluridisciplinaire de recherche sur l'environnement et les matériaux
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 Laboratoire Composants pour l?Energie

Because of its surface sensitivity, X-ray photoelectron spectroscopy allowed us to access the mechanisms at the very surface of 100 nm diameter carbon-coated LiFePO₄ nanoparticles. A continuous evolution of the Fe³⁺/Fe²⁺ ratio was observed at the surface of the particles upon charge and discharge, in good agreement with the change in the average lithium content of Li_xFePO₄ electrode material. These results support these models considering migration of a reaction front along the a-axis inside the cristallites vs. the shrinking-core model, to describe lithium (de)intercalation in LiFePO₄. XPS analyses showed also that electrode/electrolyte interface phenomena are minimized using carbon-coated LiFePO₄ particles as positive electrode material vs LiCoO₂ for instance, despite the nanometric size of the particles.

Mots clés: Carbon; Lithium batteries; X-ray; Photoelectron spectroscopy

Domaines: Matériaux

Rémi Dedryvère, Magalie Maccario, Laurence Croguennec, Frédéric Le Cras, Claude Delmas, et al.. X-Ray Photoelectron Spectroscopy investigations of carbon-coated Li_xFePO₄ materials. Chemistry of Materials, 2008, 20 (22), pp.7164-7170. ⟨10.1021/cm801995p⟩. ⟨hal-00385661⟩