Polymorphism in Li2MSiO4 ( M = Fe, Mn): a variable temperature diffraction study

A. Robert Armstrong*, Chutchamon Sirisopanaporn, Paul Adamson, Juliette Billaud, Robert Dominko, Christian Masquelier, Peter G. Bruce

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

Lithium transition metal silicates, Li2MSiO4 (M = Fe, Mn, Co), have attracted much interest as positive electrodes for Li-ion batteries due to their high theoretical capacities and their rich crystal chemistry. Low () and high () temperature forms of these tetrahedral structures differ in the ordering/distribution of cations within tetrahedral sites of an hcp based packing of oxygen. We have carried out VT powder neutron and X-ray diffraction on Li2MSiO4 (M = Fe, Mn) to characterize the rich polymorphism observed across the Li2MSiO4 (M = Fe, Mn) system as a function of temperature. For Li2FeSiO4 below 500 degrees C a (II) phase was observed with slight Li/Fe disorder. Above this temperature there was a sluggish transition to the (s) phase, which was observed up to ca. 820 degrees C, with the (II) polymorph seen at highest temperatures. Excellent agreement with phases obtained by quenching was observed, except that the phases exhibit a statistical distribution of Li/Fe, in contrast to the well-ordered structures of quenched phases. The Li2MnSiO4 polymorphism is less complex, the (II) phase is stable from room temperature to 750 degrees C, at which temperature it transforms to the structure with disordered Li/Mn.

Original languageEnglish
Pages (from-to)1043-1049
Number of pages7
JournalZeitschrift für Anorganische und Allgemeine Chemie
Volume640
Issue number6
DOIs
Publication statusPublished - May 2014

Keywords

  • Lithium
  • Transition metals
  • Silicates
  • Temperature diffraction
  • LITHIUM-ION BATTERIES
  • POSITIVE-ELECTRODE MATERIALS
  • CATHODE MATERIAL
  • ELECTROCHEMICAL PERFORMANCE
  • CRYSTAL-STRUCTURE
  • LI-ION
  • LI2FESIO4 POLYMORPHS
  • LI2MNSIO4
  • LI2COSIO4
  • LI2MNXFE1-XSIO4

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