A comparative study of Mg2+ and Li+ ion insertions into the Mo6S8 Chevrel phase using electrochemical impedance spectroscopy

M. D. Levi, H. Gizbar, E. Lancry, Y. Gofer, E. Levi, D. Aurbach

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58 Scopus citations

Abstract

A pronounced difference in the mechanism of Li and Mg-ion insertions into the Chevrel phase (MxMo6S8, 0<x<2 for Mg and 0<x<4 for Li) has been found using electrochemical impedance spectroscopy (EIS). Whereas the Li-ion insertion mechanism was qualitatively similar to that for a variety of transition metal oxides (charge-transfer semicircle+finite space Warburg), Mg-ion intercalation into the Chevrel electrode revealed two new features: a Gerischer-type impedance in the high-to-medium frequency domain and a low-frequency semicircle due to charge trapping. Evidence was provided in favor of a solid-state origin of the Gerischer impedance linked to a following chemical reaction (with respect to the Mg-ion-transfer) between the doubly charged cation and the S8 anion. Based on a transmission line representation, a more general model for charge trapping has been proposed, which reduces to a Gerischer impedance in the high frequency limit. Charge trapping (i.e., the solid-state ion association) was recognized to be the major reason for a reduced Mg-ion mobility in the Chevrel electrode compared to that of Li-ion. We also discuss a peculiar potential dependence of the resistance of ion-transfer into the Chevrel electrode in the framework of a lattice-gas model with elastic interactions and stresses in the host bulk.

Original languageEnglish
Pages (from-to)211-223
Number of pages13
JournalJournal of Electroanalytical Chemistry
Volume569
Issue number2
DOIs
StatePublished - 1 Aug 2004

Bibliographical note

Funding Information:
Partial support for this work was obtained by the Israel Science Foundation (ISF), the BMBF – the German Ministry of Science in the framework of the DIP Program, and by ATU Ltd., Israel.

Funding

Partial support for this work was obtained by the Israel Science Foundation (ISF), the BMBF – the German Ministry of Science in the framework of the DIP Program, and by ATU Ltd., Israel.

FundersFunder number
ATU Ltd.
Bundesministerium für Bildung und Forschung
Israel Science Foundation

    Keywords

    • Charge trapping
    • Charge-transfer resistance
    • EIS
    • Gerischer impedance
    • Li and Mg-ion insertion
    • MMo S Chevrel compound
    • Transmission line

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