Ionic transport in polymer electrolytes: The essential role of associated ionic species

Roger Frech, Shawna York, Harry Allcock, Clay Kellam

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Polymer electrolytes based on poly(bis(methoxyethoxyethoxy)phosphazene) (MEEP) exhibit some of the highest room temperature ionic conductivities reported in a single-phase system. The mechanism of ionic transport in polymer electrolytes, particularly the nature of the charge-carrying species, has been poorly understood at the molecular level. Vibrational spectroscopy is used to determine the nature and relative amounts of ionic species present in MEEP-LiCF 3SO 3 as a function of salt concentration. The composition corresponding to the conductivity maximum is completely dominated by neutral cation - anion contact ion pairs and the triple anion species, {Li(CF 3SO 3) 2} -. Furthermore, the conductivity changes only slightly at higher salt concentrations where triple cations dominate. These data require a dissociation - reassociation mechanism of ion transport in which dynamic equilibrium is established between the various ionically associated species by exchange of individual Li + and CF 3SO 3 - ions. The individual ions migrate between associated ionic species through the liquidlike domains defined by the entangled ethylene oxide side chains.

Original languageEnglish (US)
Pages (from-to)8699-8702
Number of pages4
Issue number23
StatePublished - Nov 16 2004

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry


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