Figure 1 shows the concentration dependency of self-diffusion coefficient ratio between (a) Li+ and G3, and (b) Li+ and [FSA]− expressed as DG3/DLi and DFSA/DLi respectively. The DG3/DLi decreased along with the increase of Li[FSA] concentration and reached unity at around 4 mol dm−3 which is equimolar composition. This indicates the formation of complex cation [Li(G3)]+, and Li+ and G3 diffuse together in the equimolar mixture. However, the DG3/DLi became lower than unity in the mixture of Li[FSA] concentration higher than 4 mol dm−3, indicating that Li+ diffuses faster than G3. In contrast, DFSA/DLi was constant around 1 at concentration lower than 4 mol dm−3 and sharply increased at higher concentration. These results suggest that the charge transport mechanism in the mixture of concertation higher than 4 mol dm−3 is different from that in the mixture of lower concertation. The [FSA]− coordinates to Li+ when excess Li[FSA] is added to G3, and forms complex anion Li[FSA]y(y−1)−. This may induce another charge transport mechanism different from the simple vehicle mechanism. It is considered that the ligand exchange of Li+ takes a significant role during the charge transport in the mixture higher than 4 mol dm−3. The Raman spectra and electrochemical properties of glyme-Li salt SILs will also be reported.
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