Evaluations of Electrical, Thermal and Electrochemical Properties on Poly(Acrylic Acid)‐Based Hydrogel Polymer Electrolyte for High Performance Electrical Double Layer Capacitor ( <scp>EDLC</scp> ) Application

ABSTRACT Hydrogel polymer electrolytes (HGPEs) composed of poly(acrylic acid) (PAA)/lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) were prepared by solution casting technique. PAA‐based HGPE exhibits a maximum ionic conductivity of (9.55 ± 0.01) mS·cm −1 at ambient temperature, upon the addition of 45 wt% LiTFSI. It follows the Arrhenius theory, indicating that a thermally activated ion‐hopping mechanism occurs through mobile ions within the PAA backbone. Apart from that, the introduction of LiTFSI salts into the PAA backbone decreases the glass transition temperature, which is proven by the findings obtained from differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) was performed to analyze the thermal stability of HGPE upon adulteration of LiTFSI. The complexation between PAA and LiTFSI in HGPEs was proven by FTIR analysis. FTIR deconvolution indicates that the most conductive HGPE contains 47% free ions. An electrical double layer capacitor (EDLC) cell was thus fabricated using the highest conducting HGPE and two identical carbon‐based electrodes. The assembled EDLC shows an increase in specific capacitance of 60.84 F/g, as illustrated in cyclic voltammetry studies. The results obtained are in good agreement with GCD findings. The fabricated EDLC using HGPE exhibits an energy density of 3.11 Wh/kg and power density of 119.62 W/kg.