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J Phys Chem B. 2017 Oct 19;121(41):9699-9707. doi: 10.1021/acs.jpcb.7b03985. Epub 2017 Oct 4.

Conductivity-Relaxation Relations in Nanocomposite Polymer Electrolytes Containing Ionic Liquid.

Author information

1
Department of Physics, Chalmers University of Technology , SE-412 96 Göteborg, Sweden.
2
Department of Chemistry and Chemical Engineering, Chalmers University of Technology , SE-412 96 Göteborg, Sweden.

Abstract

In this study, we have used nanocomposite polymer electrolytes, consisting of poly(ethylene oxide) (PEO), δ-Al2O3 nanoparticles, and lithium bis(trifluoromethanesolfonyl)imide (LiTFSI) salt (with 4 wt % δ-Al2O3 and PEO:Li ratios of 16:1 and 8:1), and added different amounts of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesolfonyl)imide (BMITFSI). The aim was to elucidate whether the ionic liquid is able to dissociate the Li-ions from the ether oxygens and thereby decouple the ionic conductivity from the segmental polymer dynamics. The results from DSC and dielectric spectroscopy show that the ionic liquid speeds up both the segmental polymer dynamics and the motion of the Li+ ions. However, a close comparison between the structural (α) relaxation process, given by the segmental polymer dynamics, and the ionic conductivity shows that the motion of the Li+ ions decouples from the segmental polymer dynamics at higher concentrations of the ionic liquid (≥20 wt %) and instead becomes more related to the viscosity of the ionic liquid. This decoupling increases with decreasing temperature. In addition to the structural α-relaxation, two more local relaxation processes, denoted β and γ, are observed. The β-relaxation becomes slightly faster at the highest concentration of the ionic liquid (at least for the lower salt concentration), whereas the γ-relaxation is unaffected by the ionic liquid, over the whole concentration range 0-40 wt %.

PMID:
28926256
DOI:
10.1021/acs.jpcb.7b03985

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