A Research On Electrode Of Flexible Supercapacitor Based On Double Layer Material

With the popularization of wearable electronics such as roll-up screens and portable devices,an increasing number of wearable energy storage devices are needed,especially the flexible supercapacitors?SCs?.As well as the basic flexibility and portability,the using of flexible SCs in military and public wearable application also requires the large capacity,high charge/discharge rate and high stability.Among all kinds of flexible substrates,fabrics based substrates have various benefits such as large surface area,intrinsically flexibility,stretch ability,showing the feasibility of system integration into wearable patterns.In this rticle,we investigated the electrode structure of flexible supercapacitors based on double electric layer materials,as well as its application.Following are main research contents in this article.1.We fabricated reduced graphene oxide?rGO?/carbon nanotubes?CNTs?nanocomposite films on the flexible fabric substrate as electrode material by repeating spaying process.We characterized the morphology of the prepared electrodes through scanning electron microscopy?SEM,Type:S-4800,Hitachi?analysis.And the electrochemical properties of electrode materials were investigated to discuss cyclic voltammetry?CV?,Galvano static charge/discharge?GCD?and Electrochemical impedance spectroscopy?EIS?.At a current density of 0.1 A/g,the specific capacitance?C_g?of rGO/CNTs composite electrodes reach to²88 F/g,which are nearly as 10times as the C_g of pure rGO or CNTs electrodes.2.Polypyrrole?PPy?film was synthesized by chemical direct oxidation polymerization and through this process the rGO/CNTs/PPy nanocomposite electrode material was prepared.The optimum process parameters were found and the influence of polymerization time and polymerization temperature on electrochemical properties of rGO/CNTs/PPy composite film was investigated.At a current density of 0.1 A/g,the C_g of rGO/CNTs/PPycomposite electrodes reach to 378.3 F/g and it can maintain good performance after bending.As expected,the doping modified polypyrrole spherical particles are closely connected to each other to form an amorphous conductive polymer.The microcosmic 3D structure forms an interconnected conductive network to transfer carriers.The electrical conductivity is fully developed in the layer.3.To preparing the poly-3,4-ethylene dioxythiophene?PEDOT?films,we usedthe vapor phase polymerization?VPP?method which is simple and highly controllable.To achieve the best performance,we systematically analyzedvarious processing conditions in the deposition process,such as polymerization time and polymerization temperature.We characterized the morphology of the prepared electrodes through scanning electron microscopy?SEM?and analyzed the contents of elements by Energy Dispersive Spectroscopy?EDS?analysis and the X-ray diffractometer?XRD?analysis.The results show that processing conditions greatly influence the properties of rGO/CNTs/PEDOT nanocomposite films.For example,when we conduct the polymerization under a 30?ambientfor 3 hours,some tiny holes appearing on the surface of rGO/CNTs/PEDOT films which greatly enlarge the specific surface areas and facilitate ions penetrating into/off the whole films.As results,the specific capacitanceof rGO/CNTs/PEDOT nanocomposite films reach up to 492 F/g.To further evaluate the rGO/CNTs/PEDOT composite electrodes in practical applications,a flexible and solid state supercapacitor based on such electrode and PVA/H₃PO₄ gel electrolyte was assembled.Devices based on this composite electrode reversibly cycle at a voltage of 1V,which provide a volume energy density of 22.8 m Wh/g and retain 98%capacitance of the initial value under a 90°bending angle.