Preparation And Electrochemical Performance Of Hierarchical PEDOT

Among the various devices,supercapacitors have many unique features,such as long cycle life,high power density and small volume,and hence attract people’s attention quickly.They now have been widely used in pacemakers,small electronic devices,electric vehicles and so on.In recent decades,conductive polymers have been broadly used as active materials in supercapacitors due to their unique structures and properties including reversibility in redox reactions,high conductivity in doped states and superior mechanical flexibility.Consequently,the combination of conductive polymers with energy storage becomes one of the most concerned interest.Aiming to prepare high-performance electrode material for supercapacitors,Poly(3,4ethylenedioxythiophene)(PEDOT)is chosen as the research object.The specific contents include:The preparation method of hierarchical petal PEDOT is as follows:using ferric chloride(FeCl3)as the oxidant and dopant,methanol as the good solvent,deionized water as the poor solvent,hierarchical flower-like PEDOT is fabricated by means of co-precipitation route in the aqueous system.The experiments indicate that the concentrations of FeCl3 and EDOT monomer,and the reaction temperature play important roles on the crystal growth mode,morphology and capacitive performance of PEDOT.Results of XRD and FT-1R indicate that with the increase of FeCl3 concentration the distances of(100)plane and(020)plane shorten while grain sizes along both the a and b axes increase,meaning the gradually ordered process of layered accumulation or the ameliorated polymerization of PEDOT.As the temperature increases,quite the opposite,the distances of(100)plane and(020)plane enlarge,and the grain size grows along the a axis but declines along b axis,corresponding to a increasingly worsen crystallinity.A petal-like hierarchical architecture with a diameter of about 1-5 μm and length of several micrometers,which maintains its morphology and possesses flexibility to some extent after being treated with 0.5 M sulfuric acid,was observed by SEM.The petal-like hierarchical structure renders PEDOT larger specific area,that enhances the contact area between the electrolyte and the active substance,shortens ions’or electrons’transport path,and thus promotes the redox reaction and rate performance of PEDOT.Moreover,the existence of room between the petals constructs a unique micro-structure,which effectively alleviates the issue of poor cycling stability that is a common issue of conductive polymers caused by volume swell/shrinkage,and therefore improves the life of the active material.The PEDOT electrodes show superior capacitive performance in the working potential range between-0.2-0.7 V.Treating with dilute acid can greatly increase their specific capacitance,for example,the capacitance of the PEDOT prepared with 0.06 g/mL of FeCl3 is 154 F/g at a discharge current density of 1 A/g.The preparation method of hierarchical coral PEDOT is as follows:choosing potassium persulfate as the oxidant,acetic acid,dilute sulfuric acid,and aluminum triflate as the dopant,hierarchical coral-like PEDOT is fabricated in the aqueous system.The experiments indicate that the amount of EDOT monomer and the type of the dopants play important roles on the crystal growth mode,morphology and capacitive performance of PEDOT.On the basis of XRD analysis,the PEDOT in different doping states has different interplanar spacing of(100)and(020)plane,correspondingly,different grain size along the a axis and the b axis.The PEDOT products are made up of coral-like blocks,and the "branches"of the corals are wrapped with numbers of tiny particles.Such a cross-linked structure greatly increases the specific areas of the polymer,that enhances the contact area between the electrolyte and the active substance,provides more conductive channels,and thus is conductive to improve the electrochemical performance of PEDOT.The mole ratio of monomer to dopant and the type of the dopant have a significant influence on the capacitance:the less the monomer,the bigger the capacitance;while among the dopants,acetic acid performs the optimum effect,followed by sulfuric acid,aluminum triflate is the worst,and the capacitive performance of PEDOT prepared with the mixture of two dopants is better than that of just single dopant.In summery,we have successfully synthesized unique hierarchical PEDOT with considerable specific capacitance(154 F/g)and excellent rate capability,and furthermore,it can be easily scaled up for mass production without the use of expensive templates or extra etching procedures,therefore providing a simple but scalable method for large-scale production of high-performance PEDOT.