Structural and transport evolution in the Li<sub>x</sub>Ag<sub>2</sub>V<sub>4</sub>O<sub>11</sub> system - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Journal of Power Sources Année : 2010

Structural and transport evolution in the LixAg2V4O11 system

Résumé

We investigated the effect of inserting lithium into Ag2V4O11 (ε-SVO) on the structure, electronic properties and redox committed by combining in situ XRD measurements, ESR spectroscopy and 4 probes DC conductivity coupled with thermopower measurements. The electrochemical discharge occurs in three consecutive steps above 2 V (vs. Li+/Li). The first one, between 0 < x < ~0.7 in Lix-SVO, has been ascribed to the V5+ reduction through a solid solution mechanism. This reduction competes with a Li+/Ag+ displacement reaction which leads to a structural collapse owing to the ionic radii mismatch between the withdrawn Ag+ and the inserted Li+. The silver reduction progresses continuously with two different slopes along two composition–potential plateaus at 2.81 V and 2.55 V. Finally, the reduction continues until we obtain an amorphous structure with V4+ and a ε of V3+. Although, the silver re-enters the structure during the subsequent recharge, the original structure is not recovered. The reduction of silver forming silver metal nano-clusters acts to increase the electronic conductivity from 3.8 × 10−5 S cm−1 to 1.4 × 10−3 S cm−1. In complement to this study, we also report on a low temperature hydro-(solvo)-thermal approach using HF(aq) as a mineralizer, which enables the synthesis of nano-sized ε-SVO particles that exhibit superior electrochemical performances compared to conventional particles synthesized by solid-state reaction.

Dates et versions

hal-00561923 , version 1 (02-02-2011)

Identifiants

Citer

F. Sauvage, V. Bodenez, H. Vezin, M. Morcrette, J.-M. Tarascon, et al.. Structural and transport evolution in the LixAg2V4O11 system. Journal of Power Sources, 2010, 195, pp.1195 - 1201. ⟨10.1016/j.jpowsour.2009.08.091⟩. ⟨hal-00561923⟩
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