Development of poly(vinyl alcohol) (PVA)/magnesium salt-based solid polymer electrolytes and its electrical double layer capacitor application

Solid polymer electrolytes (SPEs) comprising poly(vinyl alcohol) (PVA)/magnesium trifluromethanesulfonate [Mg(OTf)(2)] were prepared by the solution casting technique. The resulting PVA/Mg(OTf)(2)-based SPE exhibits the maximum ionic conductivity of (3.03 +/- 0.01)x10(-6)S/cm upon addition of 40 wt.% of Mg(OTf)(2). The PVA/Mg(OTf)(2)-based SPEs follow the Vogel-Tamman-Fulcher (VTF) theory for ionic conduction, indicating that the conduction arises from the free volume within PVA polymer chain. Besides, differential scanning calorimetry (DSC) shows a lower glass transition temperature at 55.85 degrees C after the inclusion of 40 wt.% of Mg(OTf)(2). Furthermore, FTIR analysis proves the complexation between PVA and Mg(OTf)(2 )in the SPEs. Deconvolution studies of FTIR data are also carried out to determine the percentage of free ions, ion pairs, and ion aggregates. Moreover, the electrochemical potential window improves from 3.80 to 4.77 V with the inclusion of 40 wt.% of Mg(OTf)(2). Transference number studies show that magnesium ion is the main contributor in conduction. An electrical double-layer capacitor (EDLC) was fabricated using the most conductive PVA/Mg(OTf)(2)-based SPE and two identical carbon-based electrodes to evaluate its electrochemical performance through cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis. The resulting EDLC exhibits a specific capacitance of 305 mF/g and shows electrochemical stability up to 500 cycles of charging and discharging.