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The poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) systems consisting of NaBr as a dopant salt are prepared. The stable PEO:NaBr system with 3 wt% of NaBr was subjected to low-energy ion beam irradiation to bring in morphological modification. The irradiated samples are studied using complex impedance spectra to evaluate electrical conductivity and relaxation process in the system. The studies show an increase in conductivity by one order magnitude in the irradiated systems. The dielectric loss tangent (tanδ) curves show a single peak due to strong coupling of ion transport with segmental motion. The resultant relaxation time τ exhibits a continuous decrease indicating increase in segmental dynamics as a result of increased amorphous content in the system. The temperature-dependent studies also indicate that the irradiated systems are more disordered/amorphous compared to pure systems. This fact is further supported by XRD, by observing an increase in peak width associated with reduction in peak intensity. The Raman spectra also support the change in morphology of the system by the appearance of disordered-longitudinal acoustic mode band.

Nanocomposite solid polymer electrolytes (NCSPEs) with conducting species other than Li ions are being investigated for solid-state battery applications. Pristine solid polymer electrolytes (SPEs) do not show ionic conductivity suitable for batteries. Addition of inert fillers to SPEs is known to enhance the ionic conductivity. In this paper, we present the role of silica nanoparticles in enhancing the ionic conductivity in NCSPEs with sodium as conducting species. Sodium bromide is complexed with the host polyethylene glycol polymer by solution cast method and silica nanoparticles (SiO2, average particle size 7 nm) are incorporated into the complex in small amounts. The composites are characterized by powder XRD and IR spectroscopy. Conductivity measurements are undertaken as a function of concentration of salt and also as a function of temperature using impedance spectroscopy. Addition of silica nanoparticles shows an enhancement in conductivity by 1-2 orders of magnitude. The results are discussed in terms of interaction of nanoparticles with the nonconducting anions.