Study of the capacity fading mechanism for fe-substituted LiCoO2 positive electrode

Victoria L. McLaren, Anthony R. West, Mitsuharu Tabuchi, Akiko Nakashima, Hikari Takahara, Hironori Kobayashi, Hikari Sakaebe, Hiroyuki Kageyama, Atsushi Hirano, Yasuo Takeda

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27 Citations (Scopus)

Abstract

To find the origin of a large initial irreversible capacity and capacity fading with cycling for Fe-substituted LiCoO2 (LiCo 1-yFeyO2), the LiCo0.8Fe 0.2O2 positive electrode was selected for study by ex situ X-ray diffraction, Co and Fe K-edge X-ray absorption, and 57Fe Mössbauer spectroscopies. A disordering of Fe ions from 3b(0, 0, 1/2) to 6c(0, 0, 3/8) sites was detected for initial charged samples through X-ray Rietveld analysis and Co and Fe K-edge X-ray absorption near-edge structures and extended X-ray fine structures spectra. The valence state of Fe ions in the 6c site was determined to be a 3+/4+ mixed valence state from the isomer shift values obtained by 57Fe Mössbauer spectra and mean M-O distance values. 50% of the iron ions become disordered after the initial charge process and more than 20% remain in 6c sites after the first and tenth discharge processes. The existence of Fe3-δ (0 < δ < 1) ions on the interstitial 6c site can block fast Li conduction in the Li layer of the layered rock-salt structure (R3̄m). This leads to a lack of reversibility in Fe-substituted LiCoO2 positive electrode materials.

Original languageEnglish
Pages (from-to)A672-A681
JournalJournal of the Electrochemical Society
Volume151
Issue number5
DOIs
Publication statusPublished - 2004
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

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