Preliminary study on the performance of a redox capacitor with the use of ionic liquid-based gel polymer electrolyte and polypyrrole electrodes

Kapuralage Wathsala Prasadini,Kamal P. Vidanapathirana,Kumudu S. Perera

doi:10.1007/s10854-021-06296-5

Kapuralage Wathsala Prasadini, Kamal P. Vidanapathirana + Show 1 more

Open Access

https://doi.org/10.1007/s10854-021-06296-5

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Abstract

Redox capacitor, which is one type of supercapacitor, has been attracted tremendously as it shows a satisfactory specific capacitance, good cycle ability, and good stability. The present study reveals a redox capacitor fabricated with an ionic liquid (IL)-based gel polymer electrolyte (GPE). Electrodes of the redox capacitor were fabricated with the conducting polymer, polypyrrole (PPy). The composition of the GPE was polyvinylidenefluoride–co-hexafluoropropylene (PVdF–co-HFP): 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF): ZnTF. Characterization of redox capacitor was done by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests. The relaxation time constant (τ0) of the redox capacitor is about 31.57 s implying somewhat fast redox reactions. Initial single electrode specific capacitance (CSC) was 150.2 Fg−1, and at the 500th cycle, it was 40.03 Fg−1. The decrease of the CSC may be due to the formation of the passivation layer at the GPE/electrode interface, resulting in degradation upon cycling. The GCD test resulted 48.4 Fg−1 of initial single-electrode specific discharge capacitance (Csd) value. Upon 1000 cycles, it was reached 22.3 Fg−1. The decrease of Csd may be due to the degradation of the electrode and the IL-based GPE upon prolonged cycling.

Highlights

Increasing demand for power and energy sources lead to creating a new challenge of design and fabrication of low cost, eco-friendly, and more efficient energy storage devices
SCs are classified as electrochemical double-layer capacitors (EDLCs) and redox capacitors based on their charge storage mechanism
Carbon-based electrodes are used for EDLCs and conducting polymer or transition metal electrodes are used for redox capacitors

Summary

Introduction

Increasing demand for power and energy sources lead to creating a new challenge of design and fabrication of low cost, eco-friendly, and more efficient energy storage devices In this context, supercapacitors (SCs) become attractive candidates for energy storage devices due to their higher power density when compare with the rechargeable cells and higher energy densities than conventional capacitors [1]. GPEs are prepared by trapping an ionic salt that is dissolved with polar solvent in a polymeric network These electrolytes have wide electrochemical potential windows, good conductivities, and mechanical stability still are suffering from poor electrochemical and thermal properties [9]. The present study reports the fabrication and characterization of a redox capacitor with conducting polymer, polypyrrole (PPy) based electrodes, and an IL-based GPE prepared by using 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF), zinc trifluoromethanesulfonate (Zn(CF3SO3), ZnTF), and polyvinylidene fluoride-co-hexafluoropropylene (PVdF-co-HFP). For the characterization of the fabricated redox capacitor, electrochemical impedance spectroscopy (EIS) technique, cyclic voltammetry (CV) test, and galvanostatic charge-discharge (GCD) test were performed at room temperature

Preparation of IL-based GPE

Preparation of conducting polymer electrodes

Fabrication of redox capacitor

Results and discussion

Conclusion