This work describes the performance of a gel polymer electrolyte (GPE) based redox capacitor using the cyclic voltammetry technique.GPE was prepared with 22.5 wt% polyacrylonitrile (PAN), (1:1weight ratio) ethylene carbonate (EC) and propylene carbonate (PC) having a salt concentration of 1.0 M sodium iodide (NaI). Dependence of ionic conductivity of GPE on temperature was investigated using ac impedance spectroscopy. Two polypyrrole (PPy) electrodes were used as the electrodes of the redox capacitor. The performance of the device was evaluated by cyclic voltammetry. The redox-capacitors were cycled at different scan rates to determine the scan rate at which the maximum capacitance is obtained. After tracking that scan rate, continuous cycling was carried out at that scan rate to investigate the deterioration of capacitance upon cycling. The room temperature conductivity (σ) of the GPE was 4.29 × 10 -3 S cm -1 . The conductivity variation with temperature followed the Arrhenius behavior. From the scan rates selected for the study, the maximum capacity could be obtained at the scan rate of 30 mV s -1 . The average specific capacity of the redox capacitor was 26.70 Fg -1 .

* Corresponding author ( ) economic solutions to the demand for power sources. Redoxcapacitors replace the role of batteries and conventional capacitors by hundred times of the power density and energy density. Research activities are being continued to fabricate more comprehensive supercapacitors. Among those, fabrication of the symmetric polymer capacitor is dominant because of its simplicity. In this study, the effect of polymerisation current density on the performance of a symmetric polymer redoxcapacitor is reported. Conducting polymer, polypyrrole (PPy) was used as the electrodes, while a gel polymer electrolyte as the electrolyte. Fabrication of the redox-capacitors was . They were characterised using cyclic voltammetry tests, continuous galvanostatic charge-discharge tests and electrochemical value of 12 Fg -1 could be obtained by cyclic voltammetry measurements. It was about 7 Fg -1 as per the galvanostatic stable upon continuous cycling. An increase was noticed in density. From the impedance spectroscopy measurements, it was observed that with increasing polymerisation current density, the capacitive nature of the redox-capacitors can be improved.Cyclic voltammetry, polypyrrole, redox-capacitor,

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Supercapacitors are promising alternatives for answering the thirst for ever increasing demand for power. They bridge the gap between the batteries and the conventional capacitors. Redox capacitors in the family of supercapacitors consist of conducting polymers or transition metal oxide electrodes. In this study, symmetric redox capacitors have been fabricated utilizing Polyaniline electrodes and a Polyvinylidenefluoride based gel polymer electrolyte. The effect of aniline concentration on the performance of redox capacitors was investigated. Aniline concentration was varied from 0.20 M to 0.50 M.Capacitors were characterized using Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Galvanostatic Charge-Discharge tests. Redox capacitor with 0.40 M aniline concentration showed the highest performance. From EIS measurements it was shown that the lowest relaxation time was 0.22 s. This implies that 0.40 M aniline system has the fastest ion movement behavior. Cyclic Voltammetry (CV) test of this capacitor resulted 81% of specific capacity retention between the 1 st and the 200 th cycle. Galvanostatic ChargeDischarge (GCD) for 1000 cycles showed an average discharging capacity of 323 F g -1 , power density of 760 W kg -1 and energy density of 6.5 Wh kg -1 . The results of this study confirm that aniline concentration has a significant effect on the performance of PANI films when they are served as electrodes in redox capacitors.

Gel polymer electrolytes (GPEs) have demonstrated a greater potential to be used as electrolytes for various applications such as batteries, super capacitors, electrochromic devices and dye sensitised solar cells. They consist of a salt and a mixture of solvents trapped in a polymer matrix. In this study, optimisation and characterisation of a GPE consisting of polyvinylidene fluoride, ethylene carbonate, propylene carbonate and sodium iodide and its application in a redox capacitor with two polypyrrole electrodes was studied. GPE shows a conductivity of 9.69 × 10 -3 Scm -1 at room temperature (28 °C) with good mechanical stability. The corresponding composition is 1.13 PVdF : 2.5 EC : 2.5 PC : 0.4 NaI (by weight). The variation of conductivity with temperature follows Arhenius behaviour suggesting that the conductivity mechanism takes place via hopping of ions. Conductivity is purely ionic in nature. Properties of the redox capacitors were studied by the cyclic voltammetry (CV) technique, electrochemical impedance spectroscopy (EIS) technique and galvanostatic charge-discharge (GCD) test. The CV results showed the dependency of specific capacitance on the scan rate. The EIS results showed that capacitive behaviour becomes dominant only at low frequency range. The resulting specific capacitance was 3.19 Fg -1 . It was found that the redox capacitor exhibits an average discharge specific capacitance of 5.93 Fg