Gel electrolytes with plasticizers of different polarity

Gel electrolytes were prepared by photopolymerization of oligo(ethylene glycol)(23) dimethacrylate ((EG)(23)DMA) in the presence of LiCF3SO3 and various oligo(ethylene glycol) derivatives as plasticizers. The influence of the chain length and the end groups, i.e. cyanoacetic esters, of the plasticizer on the charge carrier separation, the mobility of the ions, the conductivity of the electrolyte system and the cationic transference number t(+) was studied. Using plasticizers endcapped with polar groups, a distinct increase of the part of free ions compared with that in nonpolar plasticizers was observed by Raman spectroscopy. As a result of pulsed-field gradient NMR and electrochemical investigations including transference number measurements, we have found a strong correlation between plasticizer mobility and ion diffusion and with that, ionic conductivity. t(+) measurements indicate a relationship between the ability of the plasticizer to interact with the cations and the cationic part of charge transport.