PEDOT Solid-state Supercapacitor Assembled With Modified Gel Polymer Electrolyte

In recent years,with the great increase of energy demand and the sharp depletion of fossil fuels,the exploration of sustainable energy and the development of electrochemical energy storage/conversion technology have been increasingly intensified.Supercapacitors are becoming a new electrochemical energy storage device due to the excellent power density,cycle stability and safety,attracting a large number of researchers to competly research.Inthispaper,thepseudocapacitanceactivematerial poly(3,4-dienethiophene?PEDOT?was electrodeposited on the carbon paper?CP?with three-dimensional network structure as electrode,with redox gel polymer electrolyte and ionic liquid gel polymer electrolyte assembled into symmetrical solid-state supercapacitor,respectively.The energy density of the supercapacitor was improved from two aspects to improve the specific capacitance and boost the electrochemical voltage window.The main research contents include the following:?1?The PEDOT/CP electrode was successfully prepared by unipolar pulse method using CP as the current collector.The structure and morphology of the electrode material were characterized by Fourier transform infrared spectrometer?FTIR?and scanning electron microscopy?SEM?.The results showed that the spindle-like PEDOT nanoparticles was distributed uniformly over individual carbon fibers of the carbon paper,and PEDOT/CP retained the loose and porous microstructure of the CP,which was favorable for the migration of ion and electron.Therefore,PEDOT/CP were used as the electrodes of the following supercapacitors.?2?I^-in KI was a typical potential redox mediator due to its different oxidation/reduction states,various redox processes in the electrochemical reaction,and small ion radius,the ability to reduce the charge transfer resistance anddiffusionresistanceattheelectrode/electrolytesection.The PEDOT/CP//KI/PVA/H₂SO₄//PEDOT/CP solid-state polymer supercapacitors?SSP-SCs?were assembled using PEDOT/CP as the electrode and potassium iodide/polyvinyl alcohol/sulfuric acid?KI/PVA/H₂SO₄?as the GPE.The PEDOT SSP-SC showed high specific capacitance,outstanding energy density and good cyclestabilityfromthecyclicvoltammetry?CV?,galvanostatic charge–discharge measurements?GCD?,and electrochemical impedance spectroscopy?EIS?result.The appropriate amount of KI content and PVA concentration and electrolyte dosage can improve the ionic conductivity and pseudocapacitance of the SSP-SC,and device performance.?3?1-butyl-3-methylimidazolium tetrafluoroborate?BMIMBF₄?ionic liquid was often introduced into gel polymer electrolyte to form ionic liquid based gel polymer electrolyte with wide operating voltage window and high ionic conductivity due to its advantages of low viscosity,relatively high conductivityandeasysynthesis.Inthispaper,the1-butyl-3-methylimidazolium tetrafluoroborate/polyvinyl alcohol/sulfuric acid?BMIMBF₄/PVA/H₂SO₄?ionic liquid-based gel polymer electrolyte with 3D network structure was prepared by freeze-thawing cycle method.The symmetrical PEDOT SSP-SCs was constructed with the prepared PEDOT/CP electrodeandBMIMBF₄/PVA/H₂SO₄electrolyte.Theelectrochemical performance of SCs was tested by a series of methods.The results showed that compared with the SSP-SC of PVA/H₂SO₄ GPE,the electrochemical performance of SC of BMIMBF₄/PVA/H₂SO₄ GPE was significantly improved.Therefore,adding BMIMBF₄ to PVA/H₂SO₄ GPE can effectively improve the capacitive performance and energy density of SSP-SC.Furthermore,BMIMBF₄/PVA/H₂SO₄ GPE also has significant application value in light,thin and wearable flexible devices due to its excellent mechanical properties.