Design and characterization of bio-inspired Poly(vinyl alcohol)/Sodium alginate solid polymer electrolytes for electric double layer capacitors

Poly(vinyl alcohol) (PVA)-sodium alginate (NaAlg) solid polymer electrolytes (SPEs) were synthesized using the solution casting method. The highest ionic conductivity of ([Formula: see text])[Formula: see text]mS cm[Formula: see text] was achieved at ambient temperature upon the addition of 50 wt.% NaAlg, as determined by electrochemical impedance spectroscopy (EIS). Based on the temperature dependence of the ionic conductivity study, the ion conduction of the synthesized SPEs followed the Arrhenius principle. The complexation between the PVA and NaAlg in SPEs was confirmed by the peak shifts observed in Fourier Transform Infrared (FTIR) spectra. The ion pairing in the SPE was evaluated through FTIR deconvolution analysis. Furthermore, the thermal properties and thermal stability of the SPEs were examined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Increasing the concentration of sodium alginate also widens the electrochemical potential window. Electric double-layer capacitors (EDLCs) were fabricated using the most conductive PVA–NaAlg SPE. Upon the addition of NaAlg, the specific capacitance increased from 3.32 F/g to 11.97 F/g in the cyclic voltammetry (CV) study, while the discharge specific capacitance increased from 0.72 F/g to 9.00 F/g in the Galvanostatic Charge–Discharge (GCD) study.