Effect of Additives on the Electrical, Structural and Mechanical Property Modification of PEO-NH4HF2 based Polymer Electrolytes

Abstract

Objective: Polyethylene oxide (PEO) composed of 10 wt% ammonium bifluoride (NH4HF2) exhibited higher conductivity of 5.96x10-6 S/cm as compared to other concentrations of salt at room temperature. The effect of additives, i.e., nano-sized fumed silica concentration as nanofiller and propylene carbonate (PC) concentration as plasticizer on electrical, structural, as well as mechanical property studies of polymer electrolytes has been studied. Methods: The ionic conductivity, as well as dielectric studies of polymer electrolytes consisting of polyethylene oxide and different (x wt%) ammonium bifluoride (x=1, 2.5, 5, 10 and 15 wt %), have been measured using complex impedance spectroscopic technique. X-ray diffraction (XRD) and differential scanning calorimetry/thermogravimetric analysis (DSC/ TGA) studies have been conducted to observe the effect of additives on crystalline phase, crystallite size, melting temperature and weight loss of different polymer electrolytes. The effect of additives on the mechanical properties (tensile strength, modulus of elasticity and % elongation at break) of different polymer electrolytes has also been studied by Universal Testing Machine (UTM). Results: The maximum conductivity achieved was 1.55× 10-4 S/cm in case of plasticized nanocomposite polymer electrolytes with the simultaneous presence of 3 wt% fumed silica and 0.3 ml propylene carbonate. The variation of ionic conductivity at different temperatures and activation energy values of different polymer electrolytes were also measured and observed in good correlation. Conclusion: The observed enhancement in the ionic conductivity of polymer electrolytes with additives is due to an increase in carrier concentration, amorphous content, chain flexibility, as well as the formation of more conducting pathways. Hence, this new approach led to the development of plasticized nanocomposite polymer electrolytes with high ionic conductivity and improved structural and mechanical properties.