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 .

To supplement the ever increasing power demand in the present day world, supercapacitors have emerged as one of the suitable power storage devices. Redox capacitors have received a considerable attention due to factors such as high cycle ability, satisfactory specific capacitance and good stability. There are many reports on redox capacitors based on liquid electrolytes but these have several drawbacks. In this study, a magnesium chloride (MgCl 2 ) based gel polymer electrolyte was prepared and characterized for its suitability to be used in a redox capacitor. The composition, 0.1 polyacrylonitrile (PAN):0.4 ethylene carbonate (EC):0.4 propylene carbonate (PC):0.125 MgCl 2 (weight ratios) exhibits the highest room temperature conductivity of 4.08×10 -4 S cm -1 . Conductivity variation of this sample with the temperature shows Arrhenius behavior. The ionic transference number is 0.84. This shows that the GPE is an ionic conductor. Redox capacitors were fabricated with two polypyrrole (PPy) electrodes. They were characterized using Cyclic Voltammetry technique, Impedance Spectroscopy and Galvanostatic Charge Discharge test. Cycling at the scan rate of 10 mV/s within the potential window of -1.4 V to +1.4 V showed a specific capacitance of 120.35 F/g. Impedance data showed the electrochemical behavior of the device having resistive and capacitive behavior. Galvanostatic charge discharge test results exhibit average power density and energy density of 341 W/kg and 5 Wh/kg respectively.

* 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,

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

Solid state redox capacitors have received a tremendous interest in terms of several characteristics such as their fast energy delivery, short charging time, high power density and extended durability. Due to the absence of a liquid electrolyte, they are free from drawbacks of leakage and unsafe. In this study, preparation and characterization of a redox capacitor consisting with two identical polypyrrole (PPy): dodecylbenzenesulfonate (DBS) electrodes and a gel polymer electrolyte (GPE) based on polyvinylidene fluoride (PVdF), ethylene carbonate (EC), propylene carbonate (PC) and sodium thiocyanate (NaSCN) is reported. The GPE having the composition, 0.4 PVdF: 1 EC: 1 PC: 0.075 NaSCN (by weight) showed the maximum conductivity of 2.25× 10 -3 S cm -1 . Redox capacitors were characterized using Cyclic Voltammetry, Electrochemical Impedance Spectroscopy and Galvanostatic Charge Discharge test. They exhibited an energy density about 0.25 W h kg -1 and an average power density of 4 kW kg -1