Abstract

Electrical, thermal and Li transport properties have been measured for polyester polyol and isocyanate-based polyurethanes doped with lithium trifluoromethanesulfonimide (LiTFSI) and lithium perchlorate (LiClO 4). Electrical conductivities are estimated at 10-5- 10-6 S/cm near 300 K. The conductivities show a Vogel-Tammann-Fulcher (VTF) behavior over wide temperature ranges, characteristic of segmental polymer chain motions, and are approximately an order of magnitude larger for LiTFSI-doped than for perchlorate-doped samples. Differential scanning calorimetry (DSC) shows that Tg does not significantly depend on doping type or concentration. Room-temperature 7Li diffusivities, measured by pulsed gradient NMR, show an unexpected strong, linear increase with LiTFSI doping, but only a weak increase with LiClO4 content. These findings may indicate substantial Li clustering in the LiTFSI-doped polymers, but may also reflect the effects of doping upon interface conduction between hard and soft polymer domains. Charge carrier densities estimated from the Nernst-Einstein relation, using measured NMR diffusivity values and ionic conductivities, range from approximately 8% to 29% of total Li densities for LiTFSI, indicating that a significant fraction of Li is involved in room-temperature ionic conduction in this material. For LiCLO4 the carrier fraction is smaller, implying that Li is more tightly bound to its anion site.

Original languageEnglish (US)
Pages (from-to)1727-1731
Number of pages5
JournalSolid State Ionics
Volume181
Issue number39-40
DOIs
StatePublished - Dec 20 2010

Keywords

  • Impedance spectroscopy
  • Ionic conduction
  • Polyurethane
  • VTF

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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