Nanocomposite Polymer Electrolytes: Effect of Nanosize Fumed Silica and Plasticizers on Conductivity Behavior

Nanocomposite polymer electrolytes have been synthesized by dispersing fumed silica (with average particle size 7 nm) to polyethylene oxide (PEO) based polymer electrolytes containing ammonium bifluoride (NH₄HF₂). Although the addition of plasticizers viz. propylene carbonate (PC) and dimethyl carbonate (DMC) results in conductivity enhancement, it also leads to deterioration in mechanical properties of polymer electrolytes. However, the addition of nano size fumed silica to plasticized polymer electrolytes has been found to result in conductivity enhancement, along with better mechanical properties, and maximum conductivity of 1.55 × 10⁻⁴ S/cm (at 25 °C) has been observed, which is two orders of magnitude higher than for PEO-NH₄HF₂ (5.96 × 10−6 S/cm). The increase in free ion concentration and amorphous content with the addition of plasticizer has been studied by FTIR and XRD. The dependence of conductivity on the concentration of plasticizer, fumed silica and temperature has also been studied.