A 7Li nuclear magnetic resonance study of LiCF3SO3 complexed in poly(propylene-glycol)

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Abstract
7Li nuclear magnetic resonance (NMR) linewidths and spin–lattice relaxation times for poly(propylene‐glycol) complexed with a range of concentrations of LiCF3SO3 are reported over the temperature region from 205 to 405 K. Calculations suggest that the spin–lattice relaxation mechanism is caused by the interaction between the 7Li (I=3/2) quadrupole moment and fluctuations in the surrounding electric field gradients, whereas the line shapes are influenced by both the dipolar and quadrupolar interactions. The motional parameters reported indicate that ion–polymer or ion–ion interactions are important in determining the Li+ cation mobilities. This is reflected in the lengthening of the correlation time with increase in Li+ ion concentration which suggests a decreased mobility for the cations resulting from a transient coordination of the cation to the polymer matrix or ion aggregation. Also, the activation energies in this study (∼0.24 eV) are in agreement with values obtained from recent pulsed field gradient studies suggesting that the NMR techniques employed in this study are approriate methods for probing the dynamics of ion transport on a macroscopic scale in these materials.