Development and Characterization of Highly Ionic Conductive Hydrogel Electrolytes for Supercapacitors

In this study, epoxidized natural rubber (ENR-25) in combination with acrylamide and acrylic acid hydrogels with N,N '-methylenebis(acrylamide) as a chemical cross-linking agent was formulated using a free-radical polymerization technique. Different vol % of sodium hydroxide (NaOH) (5, 10, 15, and 20 vol %) was used to prepare the hydrogel electrolyte and labeled as NR/NaOH5, NR/NaOH10, NR/NaOH15, and NR/NaOH20, respectively. The synthesized hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). The ionic conductivity was measured using electrochemical impedance spectroscopy (EIS), and it was found that the NR/NaOH20 hydrogel obtained the highest ionic conductivity of 8.72 mS cm(-1) with the lowest activation energy of 0.1045 eV. Symmetric supercapacitors were fabricated using NR/NaOH5, NR/NaOH10, NR/NaOH15, and NR/NaOH20 as hydrogel electrolytes and electrochemical studies such as cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis were conducted. The electrochemical performance disclosed that the hydrogel containing the highest amount of NaOH (NR/NaOH(2)0) showed maximum specific capacitances of 49.66 F/g at 5 mV/s and 43.24 F/g at 300 mA/g.