Supercapacitive Properties Of PEDOT And Its Composites With MoS₂

With the ever-increasing energy consumption,energy storage and energy efficiency have become the focus of research in recent years.It is imperative to explore high-performance energy storage and conversion equipment.Among them,supercapacitors(SCs)have the advantages of fast charge and discharge,long cycle life,high power density,and environmental friendliness,making them stand out in a series of energy storage devices(such as batteries and fuel cells).Exploring electrode materials has become an indispensable part of the development of SCs.As one of the electrode materials,conducting polymers(CPs)have high charge density and low cost.Especially,poly(3,4-ethylenedioxythiophene)(PEDOT)has been recognized as an attractive material for high conductivity,low cost,excellent stability and possessing reversible electrochemical doping/dedoping ability.However,pure PEDOT is greatly restricted in application due to its relative low specific capacitance.In many literatures,most of the methods to improve the specific capacitance of PEDOT(such as molecular functionalization)have many problems such as complex steps,uncontrollable processes,and many by-products.Here,a series of PEDOT materials with different morphologies were prepared by using reverse micelle self-assembly.The mass specific capacitance of PEDOT materials was improved by adjusting the morphology;in addition,PEDOT/MoS₂ composites with different morphologies were constructed through simple electrochemical self-assembly,thus improving the area specific capacitance of PEDOT-based materials.Moreover,the morphology,structure and electrochemical properties of the as-prepared materials were studied,and the detailed research contents is as follows:(1)By precisely adjusting the ratio of sodium bis(2-ethylhexyl)sulfosuccinate(AOT)and Fe Cl₃ aqueous solution,a series of PEDOT nanomaterials with different morphologies were prepared in a reverse micelle microemulsion system.When the volume ratio(V_a/V_h)of Fe Cl₃ aqueous solution to AOT n-hexane was between 2.0×10^–2 and 3.0×10^–2,PEDOT nanoribbon,nanotubes and nanorods can be obtained,respectively.The morphologies and structures of PEDOT nanomaterials were characterized by Scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and so on.The electrochemical characterizations of PEDOT with different morphologies was carried out to analyze the influence of different morphologies on capacitance performance.When precisely controlling the volume ratio V_a/V_h was 2.7×10^–2,the PEDOT nanotubes with an inner diameter of 250-300 nm and a wall thickness of 45-70 nm can be obtained.As-obtained PEDOT nanotubes show a high specific capacitance of 171.5F g^-1 at 0.4 A g^-1,which is greater than the PEDOT nanoribbons(134 F g^-1)and nanorods(145.7 F g^-1),respectively.Additionally,the PEDOT nanotubes exhibit excellent stability with a retention rate of 105%after 5000 cycles.(2)A novel heterogeneous core/shell PEDOT@MoS₂ composite was assembled by the electrochemical co-deposition of EDOT and MoS₂ submicron spheres.The SEM,TEM images of the as-obtained composite explicitly reveal the core/shell heterostructure of PEDOT@MoS₂ with a diameter of about 800 nm.The electrochemical characterizations show that the optimized PEDOT@MoS₂ composite possesses a high specific capacitance of 2540 m F cm^-2 at 1 m A cm^-2 and excellent capacitance retention of 98.5%after 5000 cycles at a high current density of 100 m A cm^-2.The assembled PEDOT@MoS₂//PEDOT asymmetric supercapacitor shows a high energy density of 937 Wh m^-2 at 6500 W m^-2,and outstanding cycling stability with capacitance retention of 100%after 5000 cycles,which is expected to become a promising candidate for application in high-performance supercapacitors.(3)The PEDOT/MoS₂ nanocomposite is synthesized via a facile electrochemical co-deposition of the intercalation of PEDOT into flower-like MoS₂ microspheres.The SEM,TEM,and other characterizations result demonstrate the flower-like PEDOT/MoS₂ composite with an enlarged interlayer spacing of MoS₂ to 1.02 nm,in which PEDOT nanoparticles act as intercalation,and flower-like MoS₂ microspheres are used as a substrate for growth.The electrochemical characterizations indicate that the PEDOT/MoS₂ electrode has an ultra-high specific capacitance of 4418 m F cm^-2 at2 m A cm^-2 and remarkable cycling stability,retaining 100%of the initial capacitance at a high current density of 100 m A cm^-2 after 10000 cycles.The symmetric PEDOT/MoS₂supercapacitor presents a high energy density of 88.3 m Wh cm^-2 at 60m W cm^-2,and outstanding cycling stability(93%after 10000 cycles).These prominent electrochemical performances are attributed to the expanded interlayer spacing,the synergistic effect between PEDOT and MoS₂,the low resistance,along the PEDOT/MoS₂ porous structure.