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Room temperature fast-ion conduction in imidazolium halide salts

journal contribution
posted on 01.01.2001, 00:00 authored by H Every, A Bishop, D MacFarlane, G Orädd, Maria ForsythMaria Forsyth
Fast-ion conduction has been observed in the iodide and bromide salts of 1-methyl-3-ethylimidazolium at ambient temperatures. The melting point of these two compounds is above 350 K and even at 273 K the ionic conductivity in the solid-state is greater than 10−3S cm−1. Cation diffusion coefficients have been measured using fringe field gradient and/or pulse field gradient 1H NMR techniques, which indicated cation diffusion coefficients of the order of 10−10 m2 s−1 in the solid-state. Remarkably, these values are up to an order of magnitude higher than the cation diffusion coefficient in the supercooled liquid at 293 K. The activation energy for diffusion in the solid-state is extremely small, as is typical of solid-state fast-ion conductors and indicates a change in transport mechanism from the melt to the crystal. The inability to detect an 127I signal together with the modelling of the conductivity using the Nernst–Einstein equation suggests that the solid-state conduction is primarily due to cation diffusion. The solid-state fast-ion conduction is most likely related to vacancy diffusion along the cation layers in the crystal. The temperature dependence of the NMR signal intensity indicates that the number of mobile species is increasing with increasing temperature with an activation energy of approximately 20–30 kJ mol−1.

History

Journal

Journal of materials chemistry

Volume

11

Issue

12

Pagination

3031 - 3036

Publisher

Royal Society of Chemistry

Location

Cambridge, England

ISSN

0959-9428

eISSN

1364-5501

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2001, Royal Society of Chemistry