Correlation of self-diffusivity and ionic conductivity in gel electrolytes on basis of oligo(ethylene glycol)n-dimethacrylate

The relation between the ionic conductivity and the charge carrier diffusivity of an electrolyte is given by the Nernst-Einstein equation. However, this equation is in disagreement with data in the field of polymer electrolytes. We have measured the ionic conductivity of different liquid and gel electrolytes and the self-diffusivity of the plasticizer, the Li-containing, and the F-containing species by pulsed field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The results are discussed in terms of a modified Nernst-Einstein equation, considering that only charged ionic species contribute to the conductivity whereas PFG-NMR measures the self-diffusivity of charged as well as noncharged species. (C) 1998 Elsevier Science B.V. All rights reserved.