A new aspect of Chevrel compounds as positive electrodes for magnesium batteries

T. Ichitsubo, S. Yagi, R. Nakamura, Y. Ichikawa, S. Okamoto, K. Sugimura, T. Kawaguchi, A. Kitada, M. Oishi, T. Doi, E. Matsubara

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

Chevrel compounds are regarded as potential positive-electrode materials for magnesium rechargeable batteries, but their redox potential is only about 1.2 V vs. Mg/Mg2+. In this work, we show logically and experimentally that the redox potential of Chevrel compounds can be as high as about 2-3 V vs. Mg/Mg2+. A crucial basis for this is that Cu cations can be extracted from CuxMo6S8 at around 1.2-1.6 V vs. Mg/Mg2+ in the conventional electrolyte (Grignard-reagent/ tetrahydrofuran) while the anodic dissolution of Cu metal can occur above about 1.7 V vs. Mg/Mg2+ in the same electrolyte, which means that the chemical potential of Cu in Chevrel compounds is higher than that in pure Cu metal. This thermodynamic conflict inevitably compels us to consider a certain interaction with the solvent, rather than simple deintercalation from the compound, which is discussed throughout the paper. With the use of large-molecule solvents or ionic liquids, we have observed an intriguing relaxation phenomenon, where the cations move to find more stable sites, which directly indicates that the Chevrel compounds have several sites for cations.

Original languageEnglish
Pages (from-to)14858-14866
Number of pages9
JournalJournal of Materials Chemistry A
Volume2
Issue number36
DOIs
Publication statusPublished - 2014 Sep 28
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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