Ionic Conductivity-Structure Property Relationship in Gel Electrolytes on the Basis of Oligo(ethylene glycol)↓(23) Dimethacrylate Plasticized with Oligo (ethylene glycol)↓(11) Dimethyl Ether

摘要

This paper reports dielectric spectroscopic studies completed by electrochemical measurements in combination with DSC and PFG-NMR investigations to study the charge carrier transport in gel electrolytes, which were prepared by photoinitiated polymerization of oligo(ethylene glycol)↓(23) dimethacrylate [(EG)↓(23)DMA] in the presence of oligo(ethylene glycol)↓(11)dimethyl ether [(EG)↓(11)DME] as plasticizer and LiCF↓(3)SO↓(3). The resulting films show a glass transition at about -60 ℃ and the melting of the plasticizer around -12 ℃. Below the glass transition two relaxation processes were observed by dielectric spectroscopy, which most likely are to be related to the 7 relaxation of the EG groups and the β relaxation of the methacrylate groups. The high-temperature behavior of the dielectric response is dominated by the conductivity, which is weakly dependent on the frequency in this temperature range. The permittivity goes through a maximum at room temperature and decreases with further enhancement of the temperature in connection with an increase in ionic aggregation indicated by growing deviations from the Nernst-Einstein relationship. These deviations expressed as a Haven ratio are discussed as the contribution of bounded species that do not take part in the conductivity to the overall diffusivity, either by an enlarged content of these species, C ↓(b), or by an enhancement of their self-diffusivity, D↓(b).