Determination of the interaction within polyester-based solid polymer electrolyte using FTIR spectroscopy

Characterization and interaction behavior between Li+ ion and CO groups of a series polyester electrolyte have been thoroughly examined using Fourier transform infrared (FTIR). The “free/Li+ bonded” CO absorptivity coefficient of the LiClO4/polyester can be determined quantitatively using FTIR spectrum ranging from 1800 to 1650 cm−1 at 80 °C. Results from curve fitting show that the “free/Li+ bonded” CO absorptivity coefficient is 0.144 ± 0.005. The CO group of polymer electrolyte shows strong interaction with Li+ ion and a limit value of 95% “Li+ bonded” CO is approached in the polymer electrolyte system when the Li+ ion equivalent fraction is about 0.28. The molecular structure of polyester electrolyte does not affect significantly the efficiency of interaction between Li+ ion and CO.