Nuclear magnetic resonance and conductivity study of HEC/polyether-based polymer electrolytes

Measurements of H-1 and Li-7 nuclear magnetic resonance (NMR) and ionic con ductivity are reported for the polymer electrolytes formed by hydroxyethylc elluloses (HEC), poly(ethylene oxide) diisocyanate (DPEO) and LiClO4. The N MR experiments exhibit the qualitative features associated with Li+ and pol ymer chain mobilities in polymer electrolytes, namely the presence of well- defined Li-7 and H-1 spin-lattice relaxation rate maxima (T-1(-1)). The sin gle absorption band in the proton spectra and the observed H-1 and Li-7 exp onential relaxation indicate that the HEC/DPEO/LiClO4 polymer electrolytes are predominantly amorphous. The conductivity values obtained by a.c. measu rements rise above 10(-4) S/cm at 370 K and are slightly higher for the sam ples with a greater oxygen content in the HEC molecule. The parameters esti mated from the data indicate that the conductivity and the mobilities of Li + and polymer chains are comparable to those found in the PEO8LiClO4 polyme r electrolyte. (C) 2001 Elsevier Science Ltd. All rights reserved.