Kinetics of electrochemical insertion of lithium into WO》.pdfVIP

SOLID Solid State Ionics 70/71 (1994) 45 l-457 STATE North-Holland IOWNS Kinetics of electrochemical insertion of lithium into WO Naoaki Kumagai, Maroka Abe ‘, Nobulo Kumagai, Kazuo Tanno Department ofApplied Chemistry and Molecular Science, Faculty ofEngineering, Iwate University, Morioka 020, Japan J.P. Pereira-Ramos Laboratoire d’Electrochimie, Catalyse et Synthese Organic, CNRS UMR28, 2 rue Henri-Dunant, 94320 Thiais, France A kinetic study of the electrochemical insertion of lithium into the original form of WO,, formed by the heat-treatment of H2W04 at 448 K, were carried out using an ac impedance method. The chemical diffusion coefficients, 6, of lithium in the oxide were measured as functions ofthe lithium composition and temperature by using several kinds of electrolytes. The obtained values of fi, based on a geometric surface area, depended strongly on the lithium composition and the kind of electrolytes. The dvalues, obtainedusing 1MLiC104and 1MLiAsFBsolutions ofpropylenecarbonate, wereoftheorder of lo-” cm/s at 298 Kfor 0.2x 1.0 in LiXW03, corresponding to a lithium self-diffusion coefficient of the order of lo-‘* cm*/s, while using the 1M LiBF., and 1M LiPFs solutions considerably lower values of d, 10-‘3-10-‘2 cm’/s, were obtained for 0.2 XX 1.O.The activation energy for the diffusion of lithium in W03 o