NMR and Raman studies of a novel fast-ion-conducting polymer-in-salt electrolyte based on LiCF3SO3 and PAN
Data(s) |
03/01/2000
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Resumo |
We report spectroscopic results from investigations of a novel solid polymeric fast-ion-conductor based on poly(acrylonitrile), (PAN, of repeat unit [CH<sub>2</sub>CH(CN)]<sub><i>n</i></sub>), and the salt LiCF<sub>3</sub>SO<b>3</b> . From NMR studies of the temperature and concentration dependencies of <sup>7</sup>Li- and <sup>l</sup>H-NMR linewidths, we conclude that significant ionic motion occurs at temperatures close to the glass transition temperature of these <i>polymer-in-salt</i> electrolytes, in accordance with a recent report on the ionic conductivity. In the dilute <i>salt-in-polymer</i> 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<sup>+</sup>–PAN interaction. The characteristic δ<sub>s</sub>(CF<sub>3</sub>) mode of the CF<sub>3</sub>SO<sub>3</sub><sup>−</sup> anion at <sub>~</sub>750–780 cm<sup>−l</sup> 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<sub>~</sub>60–10:1). A strong Li<sup>+</sup>–PAN interaction is manifested as a pronounced shift of the characteristic polymer C=N stretching mode, found at <sub>~</sub>2244 cm<sup>−l </sup>in pure PAN, to <sub>~</sub>2275 cm<sup>−l</sup> for Li<sup>+</sup>-coordinated C=N moieties. Our proton-NMR data suggest that upon complexation of PAN with LiCF<b>3</b> SO<sub>3</sub>, the glass transition occurs at progressively lower temperatures.<br /> |
Identificador | |
Idioma(s) |
eng |
Publicador |
Elsevier Science Pub. Co. |
Relação |
http://dro.deakin.edu.au/eserv/DU:30030115/forsyth-nmrandraman-2000.pdf http://dx.doi.org/10.1016/S0013-4686(99)00386-2 |
Direitos |
2000, Elsevier Science Ltd. |
Palavras-Chave | #polymer-in-salt electrolyte #lithium and proton NMR #FT-Raman spectroscopy #poly(acrylonitrile) #LiCF3SO3 |
Tipo |
Journal Article |