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Mass and Charge Transport in the Polymer-Ionic-Liquid System PEO-EMImI: From Ionic-Liquid-in-Polymer to Polymer-in-Ionic-Liquid Electrolytes.

Authors
Type
Published Article
Journal
The Journal of Physical Chemistry B
1520-5207
Publisher
American Chemical Society
Publication Date
Volume
119
Issue
17
Pages
5693–5700
Identifiers
DOI: 10.1021/acs.jpcb.5b01113
PMID: 25848686
Source
Medline
License
Unknown

Abstract

Conventional polymer electrolytes based on inorganic salts are commonly characterized and utilized over a small salt-poor composition range because of phase transitions accompanied by loss of ion conductivity at high salt concentrations. By contrast, well-chosen polymer-ionic-liquid (IL) systems offer the possibility to vary the IL content from the IL-in-polymer to the polymer-in-IL domain. We have investigated the temperature-dependent ionic conductivity in PEOyEMImI systems consisting of poly(ethylene oxide) complexed with 1-ethyl-3-methylimidazolium iodide for y = EO/IL ratios ranging from 0.6 to 60 and compared diffusivity data with that arising from (1)H pulsed-field-gradient nuclear magnetic resonance for EMIm and (125)I radiotracer diffusion for iodine. Surprisingly, the diffusivity of cations and anions vary at most by 50% at fixed temperatures over the entire composition range. The much larger changes in the charge diffusivity Dσ relate to ion pairing exhibiting a minimum near the intermediate composition y = 10. Altogether, the results are relevant to application in dye-sensitized solar cells and show that a high ion density is crucial to enhance the iodine transport capacity.

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