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- Ferry, Anders, et al.
(författare)
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NMR and Raman studies of a novel fast-ion-conducting polymer-in-salt electrolyte based on LiCF3SO3 and PAN
- 2000
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 45:8-9, s. 1237-1242
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Tidskriftsartikel (refereegranskat)abstract
- We report spectroscopic results from investigations of a novel solid polymeric fast-ion-conductor based on poly(acrylonitrile), (PAN, of repeat unit [CH2CH(CN)]n), and the salt LiCF3SO3. From NMR studies of the temperature and concentration dependencies of 7Li- and 1H-NMR linewidths, we conclude that significant ionic motion occurs at temperatures close to the glass transition temperature of these polymer-in-salt electrolytes, in accordance with a recent report on the ionic conductivity. In the dilute salt-in-polymer regime, however, ionic motion appears mainly to be confined to local salt-rich domains, as determined from the dramatic composition dependence of the ionic conductivity. FT-Raman spectroscopy is used to directly probe the local chemical anionic environment, as well as the Li+-PAN interaction. The characteristic δs(CF3) mode of the CF3SO3- anion at ∼ 750-780 cm-1 shows that the ionic substructure is highly complex. Notably, no spectroscopic evidence of free anions is found even at relatively salt-depleted compositions (e.g. N:Li ∼ 60-10:1). A strong Li+-PAN interaction is manifested as a pronounced shift of the characteristic polymer C=N stretching mode, found at ∼2244 cm-1 in pure PAN, to ∼ 2275 cm-1 for Li+-coordinated C=N moieties. Our proton-NMR data suggest that upon complexation of PAN with LiCF3SO3, the glass transition occurs at progressively lower temperatures.
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