Competition between the plasticizer and polymer on associating with Li+ ions in polyacrylonitrile-based electrolytes

The Raman and infrared spectra of the systems of plasticizer/LiClO4 and plasticizer/polyacrylonitrile (PAN)/LiClO4 have been recorded, where the plasticizer includes dimethylformamide (DMF) and propylene carbonate (PC). By comparing the spectra. it is found that the association of Li+ ion is more competitive with DMF than with PC in the Liquid or gel electrolytes. Moreover the addition of PAN into DMF/LiClO4 solution has less influence on the Li+-solvent association than into PC/LiClO4 solution. Although a strong interaction has been observed between Li+ ions and PAN in PC/LiClO4/PAN electrolytes, no similar interaction is observed between Li+ ion and PAN in DMF/PAN/LiClO4 system. However. after the plasticizer is removed from the gel electrolytes, apparent interaction is observed between Li ion and PAN. These phenomena lead to a conclusion that there is a competition between the plasticizer and the polymer for association with the Li+ ions in the PAN based electrolytes. In addition, it is found that the multiple ion aggregates are formed without the appearance of the usual ''solvent-shared ion aggregates'' in the plasticizer-free electrolyte, which suggests that the Li+ ions may move both in the gel state and with the segmental chain of PAN while the ClO4- anion migrates mainly in the gel state in a practical PAN-based electrolyte.