Lix(Mn1-yCoy)O 2 intercalation compounds as electrodes for lithium batteries: influence of ion exchange on structure and performance

AD Robertson, AR Armstrong, AJ Fowkes, Peter George Bruce

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)

Abstract

LixMn1-yCoyO2 compounds were synthesised by a low temperature route involving ion exchange from sodium precursors. Neutron diffraction confirmed that the structures are layered (space group R (3) over barm). Materials synthesised from the precursors by ion exchange using LiBr in ethanol at 80 degreesC possess vacancies on the transition metal sites which pin residual Na+ ions. Such transition metal vacancies and Na+ ions are not observed on refluxing at 160 degreesC in hexanol. We show that lithium intercalation accompanies the ion exchange process. The presence of Na+ in the Li+ layered materials induces disorder perpendicular to the layers and this has been modelled. The performance of the materials depends on the ion exchange conditions. The y = 0.025 compound obtained in ethanol exhibits a particularly high capacity to cycle lithium. The initial discharge capacity is 200 mA h g(-1) with a fade rate of only 0.08% per charge/discharge cycle on extended cycling. This performance is delivered despite conversion to a spinel-like phase during cycling and is markedly superior to the cycling ability of directly prepared spinels over a similar composition range.

Original languageEnglish
Pages (from-to)113-118
Number of pages6
JournalJournal of Materials Chemistry
Volume11
Publication statusPublished - 2001

Keywords

  • LAYERED LIMNO2
  • POSITIVE ELECTRODE
  • CATHODE MATERIALS
  • LIMN2O4
  • LI
  • LI(MN1-YCOY)O-2
  • FAULTS

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