Solid-state supercapacitor with impressive performance characteristics, assembled using redox-mediated gel polymer electrolyte

A solid-state supercapacitor is assembled using redox-mediated gel polymer as the electrolyte and separator and coconut shell-derived, steam-activated carbon as the electrodes. The gel polymer electrolyte (GPE) is based on poly(vinyl alcohol) (PVA)-potassium hydroxide (KOH)-hydroquinone (HQ), and is obtained using solution casting technique. Amorphous nature of the GPE is confirmed from XRD studies and the complex formation in the GPE is confirmed from FTIR spectral analysis. The GPE films are electrochemically characterized using impedance analysis, cyclic voltammetry and galvanostatic charge/discharge test. Self-discharge studies of the assembled supercapacitor are also carried out. Higher ionic conductivity around 53 mS cm(-1) and superior flexibility serve as the main advantages of this redox-mediated GPE. The electrode-specific capacitance of the supercapacitor is found to be as high as 326.53 F g(-1) with a capacity retention of 84.2% after being subjected 1000 charge-discharge cycles at a current density of 0.8 A g(-1). The assembled supercapacitors are found to offer quite high energy density and power density around 33.15 Wh kg(-1) and 689.58 W kg(-1), respectively. These types of redox-mediated, flexible, gel polymer electrolytes are desirable for designing high power solid-state supercapacitors for energy storage applications.