Flexible Supercapacitor Based On High Performance Composite Fiber

Fiber-based flexible energy storage devices have received close attention from scientific research and industry in recent years due to their obvious advantages and wide application.Different from traditional lithium ion batteries and supercapacitors,flexible energy storage devices should not only have advantages of high energy density,high power density,high window voltage,but also have excellent multiplier performance and long-term cycle.Although the development of flexible energy storage devices in recent years is considerable,they are also facing a series of challenges in the future development and industrialization process:(1)improve the mechanical properties of materials.(2)develop new preparation technologies.(3)design new structure.(4)develop new flexible electrodes.This makes the fabrication of flexible energy storage devices extremely challenging.In order to improve the mechanical properties of materials,flexible energy storage devices should have small size,high flexibility,light weight,strong mechanical properties while meeting excellent electrochemical properties.In this project,high-strength ultra-high molecular weight polyethylene fibers are used as flexible substrates,and dopamine,silver and poly(3,4-ethylenedioxythiophene-polystyrene sulfonic acid)are coated on the surfaces of the flexible substrates in sequence to improve the characteristics of surface inertness,non-conductivity and low capacitance,thus preparing flexible fiber electrodes with high strength.The fiber electrode has a strength of 3.72 GPa,an area specific capacitance of 563 mF cm-2 at a current density of 0.17 mA cm-2,and an energy density of 50.1 μWh cm-2 at a power density of 124 μW cm-2.In addition,the capacitance of the capacitor is only reduced by 8%after being continuously bent for 1000 times.Under the tensile strength of 3.55 GPa,its capacitance can still be kept at 75%.UHMWPE/PDA/Ag/PEDOT FSC has excellent electrochemical and mechanical properties.As the industrial production and preparation methods of electrode materials are also getting more and more attention,develop or improve new types of preparation is crucial.This project uses carbon cloth as flexible substrate,and prepares flexible electrode materials through a convenient,scalable production and one-step electrodeposition method.Fe2O3 was used as the negative electrode material and MnO2-PEDOT was used as the positive electrode material to assemble the planar asymmetric supercapacitor.The preparation of positive and negative electrode materials can be completed in a few minutes.More importantly,this simple and green electrochemical deposition method can be designed as a continuous preparation process.The voltage of the flexible asymmetric supercapacitor can be increased to 2 V,the energy density reaches 0.34 mWh cm-3 at a power density of 121.2 mW cm-3.The capacitance can still be kept above 95%after 1000 times of continuous bending,and drive electronic watches and 41 LED lights.This one-step co-deposition method can be used to produce simple,rapid and large-scale materials,and electrochemical method lays a foundation for rapid preparation.This method can ensure the uniformity and stability of materials in large-scale production.Therefore,this method of continuous preparation on a large scale not only has certain research value,but also provides the possibility for industrialization.Metal oxides and conductive polymers are common and important electrode materials,which can endow substrate materials with high capacitance and high conductivity.Ordinary composite materials are prepared by layer-by-layer coating,which is rather complicated.Therefore,improving a new and efficient preparation method has certain research value.In this project,carbon fiber cloth is used as flexible substrate,and metal oxide MnO2,Co3O4 and conductive polymer Ppy,PEDOT are simultaneously loaded on the substrate by constant current co-deposition and cyclic voltammetry co-deposition.Compared with other composite preparation methods,this method is efficient and simple.Compared with the conventional layer-by-layer composite material,the meta oxide-conductive polymer composite material has more excellent and stable electrochemical performance.The electrode MnO2-Ppy and MnO2-PEDOT had the areal capacitance of 470 mF cm-2 and 365 mF cm-2 respectively at the current density of 0.1 mA Cm-2.Under the current density of 0.1 mA cm-2,Co3O4-Ppy and Co3O4-PEDOT had the areal apacitance of 900 mF cm-2 and 1080 mF cm-2,respectively.After 10000 long cycles test,the capacitance retention rate remained above 90%.In addition,the symmetrical flexible supercapacitor assembled with PVA/LiCl gel electrolyte also has excellent electrochemical properties.At the power density of 90.9 mWh cm-3,it can reach the energy density of 0.255 mWh cm-3.After 10000 cycles of charge and discharge,the capacitance retention rate can be maintained above 90%.