Ion transport studies in PEO:NH4ClO4 polymer electrolyte and its composite with Al2O3

Composition, temperature and humidity dependence of ionic conductivity in polyethylene oxide (PEO):NH4ClO4 polymer electrolyte composite obtained by the dispersal of Al2O3 is reported. The dispersal of Al2O3 introduces significant changes in the conductivity vs. composition isotherm. The conductivity of the composite peaks at two concentrations of Al2O3 is ~2 × 10−5 S cm−1. For studying ion dynamics, motional narrowing of 1H NMR line with temperature is also reported. In PEO:NH4ClO4 (without dispersed Al2O3), two 1H frequency-shifted NMR lines are seen (one of these have been assigned to the 1H belonging to –CH2–CH2– chain of the polymer and the other to NH4+ complexed with the chain). For the (PEO:NH4ClO4) + Al2O3 composites, however, one additional narrow peak is also seen at temperatures higher than 40 °C. This has been interpreted in terms of some hopping H+ ions getting loosely bonded to Al2O3, forming Al(OH)3, which possibly releases an additional mobile protonic species (OH−).