Effect of Mixed Ions and Ion Irradiation on Ionic Conductivity of Solid Polymer Electrolytes

It is a well known fact that conductivity in case of solid polymer electrolytes (SPEs) is due to hopping of ions assisted by the segmental motion of polymer chains. It is observed that the ionic conductivity in SPEs increases with increase in the concentration of ions. After certain critical concentration the conductivity starts decreasing due to the formation of ion pairs. In this work, an attempt is made to identify the concentration at which ion pair formation occurs and hence improve conductivity by incorporating two different ions (salts) in the polymer matrix. SPEs with mixed conducting species PEO_xLiBr_yNaBr with different concentration of salts have been prepared and investigated. Also an attempt is made to modify the crystalline phase of the host polymer by low energy ion beam (Oxygen ion, O⁺¹ with energy 100 keV) irradiation. These observations place ion irradiation as an effective tool in improving ionic conductivity in SPEs. Using X-ray diffraction spectra and the temperature dependent conductivity studies of SPEs, the effect of mixed ions and ion irradiation on the ionic conductivity of SPEs is investigated and presented.