Electrochemical kinetics of nanostructure LiFePO4/graphitic carbon electrodes

Kazuaki Kisu (1) , Etsuro Iwama (1) , Wako Naoi (2) , Patrice Simon (1, 3, 4) , Katsuhiko Naoi (1, 2)

1 TUAT - Tokyo University of Agriculture and Technology
2 K & W Inc. (JAPAN)
3 RS2E - Réseau sur le stockage électrochimique de l'énergie
4 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux

Lithium cation insertion/deinsertion reaction kinetics in a LiFePO4 (LFP)/graphitic carbon composite material were electrochemically studied with a cavity microelectrode (CME). The LFP/graphitic carbon composite has a core LFP (crystalline/amorphous)/graphitic carbon shell structure. In the crystalline and amorphous LFP phase, different reaction mechanisms were observed and characterized. While the reaction mechanism in the crystalline LFP phase is controlled by Li+ diffusion, the amorphous LFP phase shows a fast, surface-controlled, pseudocapacitive charge-storage mechanism. This pseudocapacitive behavior is extrinsic in origin since it comes from the presence of Fe3 + defects in the structure. These features explain the ultrafast performance of the material which offers interesting opportunities as a positive electrode for assembling high power and high energy hybrid supercapacitors.

Mots clés: Defective lithium iron phosphate; Core/shell structure; Pseudocapacitive behavior; Ultrafast performance; Hybrid supercapacitor; Cavity microelectrode

Domaines: Matériaux; Autre

Kazuaki Kisu, Etsuro Iwama, Wako Naoi, Patrice Simon, Katsuhiko Naoi. Electrochemical kinetics of nanostructure LiFePO4/graphitic carbon electrodes. Electrochemistry Communications, 2016, 72, pp.10-14. ⟨10.1016/j.elecom.2016.08.013⟩. ⟨hal-01457541⟩