Abstract
In this work, solid-state polymer supercapacitor (SSC) was assembled using poly(3,4-ethylenedioxythiophene/carbon paper (PEDOT/CP) as an electrode and ionic liquid (1-butyl-3-methylimidazole tetrafluoroborate)/polyvinyl alcohol/sulfuric acid (IL/PVA/H2SO4) as a gel polymer electrolyte (GPE). The GPE was treated through freezing–thawing (F/T) cycles to improve the electrochemical properties of PEDOT SSC. Cyclic voltammetry (CV), galvanostatic charge–discharge measurements (GCD) and electrochemical impedance spectroscopy (EIS) techniques and conductivity were carried out to study the electrochemical performance. The results showed that the SSC based on ionic liquid GPE (SSC-IL/PVA/H2SO4) has a higher specific capacitance (with the value of 86.81 F/g at 1 mA/cm2) than the SSC-PVA/H2SO4.The number of F/T cycles has a great effect on the electrochemical performance of the device. The energy density of the SSC treated with 3 F/T cycles was significantly improved, reaching 176.90 Wh/kg. Compared with the traditional electrolytes, IL GPE has the advantages of high ionic conductivity, less volatility, non-flammability and wider potential window. Moreover, the IL GPE has excellent elastic recovery and self-healing performance, leading to its great potential applications in flexible or smart energy storage equipment.
Highlights
Electrochemical energy storage devices have received much attention due to the increasing population and the sharp depletion of fossil fuels [1,2,3,4]
To obtain the excellent properties, we study the effect of the number of F/T cycles on the state polymer supercapacitor (SSC)
For sample F/T-1, the peak observed at 100 °C is considered as a polymer chains entanglement act as knots [53,54], while the pores are filled by the ionic liquid, H2 SO4 chain movement caused by water or acid, IL molecules release or movement
Summary
Electrochemical energy storage devices have received much attention due to the increasing population and the sharp depletion of fossil fuels [1,2,3,4]. Supercapacitors (SCs) are a promising green energy storage device because of their high power density, fast charge–discharge rate, long-cycle stability, and eco-friendliness [5,6,7,8,9,10]. Polymers 2020, 12, 297 diffusive transport properties of liquids [17,18] They have the advantages of high ionic conductivity, easy design configuration, flexibility or self-healing [19], which provides promising ways to design high-performance and multi-functional SCs. despite the great progress which has been made with GPEs, their low energy density and specific capacitance are still major issues that limit their practical applications. Some studies have reported the symmetrical supercapacitors based on IL GPE and their electrochemical performance, most of them used inorganic active carbon materials or metal oxides as electrodes. It has great potential applications in small, flexible, and smart energy-storage devices
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