Construction And Performance Study Of Flexible/wearable Fiber-shaped Supercapacitors

The rapid development of portable and wearable electronics in recent years has boosted the demand for appropriate flexible and lightweight energy supply devices.Supercapacitors(SCs)have attracted significant interest during the past few decades because of their high power density,super-long cycling life and safe operation.By offering,rapid charging and discharging rates,and the ability to sustain millions of cycles.SCs bridge the gap between batteries and conventional electrolytic capacitors.As a new member of SCs,fiber SCs(FSCs)have attracted considerable attention since 2011 and have shown great potential in miniaturized consumer electronics,wearable electronics and smart textiles.Due to their unique wire-shaped structure.FSCs can be deformed into desired shapes and even knitted into wearable textiles/fabrics.Furthermore,compared with conventional bulk SCs,FSCs could be easily integrated with photovoltaic devices,detectors or sensors to form self-powered or multifunctional integrated systems.However,compared to conventional SCs.research on FSCs is still in its infancy and it remains challenging to increase the energy density without sacrificing power density and cycling life.A common research goal is to develop flexible FSCs while preserving or even surpassing their electrochemical characteristics as compared to conventional SCs.1.A fiber-shaped asymmetric supercapacitor(FASC)with high energy density has been developed successfully using CNT@ZnO-NWs@MnO2 fibers as the positive electrode and CNT fibers as the negative electrode.Due to the high capacitances and excellent rate performances of CNT@ZnO-NWs@MnO2 fibers and CNT fibers,such an asymmetric cell exhibits superior electrochemical performances.An optimized FASC can be cycled reversibly in the voltage range of 0-1.8 V,and exhibits a maximum energy density of 13.25 mWh cm-2,which is much higher than those reported for fiber-shaped supercapacitors.Owing to the rational structure design,the all-solid-state FASCs demonstrate excellent mechanical and electrochemical stability.Over 1000 bending cycles,96.7%of the initial capacitance can still be retained.2.The PANI/graphene porous composite film was deposited on the surface of CNT fibers by electrochemical polymerization,and the PANI/graphene@CNT fiber composite electrode was successfully prepared.Graphene is very helpful to improved the electrochemical performance of the composite electrode(eg.rate performance,cycle stability).Based on the charge balance principle,an asymmetric fiber-shaped supercapacitor was successfully constructed.It resulted in excellent performances including an extended operating voltage window of 1.6 V,a maximum energy density of 160 ?Wh cm-2 at power density of 13 mW cm-2.3.We first fabricated threedimensional CNT sponge(3DCS)by a facile electrochemical activation and freeze-drying method and then synthesized 3DCS/polyaniline nanocomposite fibers by in situ electro-polymerization.Through a rational nanoscale electrode engineering design,the resultant fibers show a specific capacitance as high as 242.9 F cm-1 in 1 M H2SO4.Furthermore,a fiber-shaped asymmetric supercapacitor(FASC)was assembled using 3DCS/P as the positive electrode and 3DCS as the negative electrode.After optimization,the FASC delivers a high energy density of 30.92 mWh cm-2,which is about 2 times higher than that of the highest reported previously,and maintains a maximum power density(1.78 mW cm-2)more than two orders of magnitude higher than those of micro-batteries and an outstanding mechanical stability with 90.2%specific capacitance retained after 1000 bending cycles.In view of the excellent electrochemical characteristics and the simple manufacturing of the highly conductive and flexible 3DCS/P,it offers new opportunities for designing long-life wearable FSCs with high energy density and high power density.4.We report a facile method to prepare a novel fibrous CNT-aerogel by electrochemical activation and freeze-drying.The fibrous CNT-aerogel electrode possesses large specific surface area,high mechanical strength,excellent electrical conductivity,as well as a high specific capacitance of 160.8 F g-1 at 0.5 mA and long cyclic stability.Then we assembled a non-faradaic FSC based on fibrous CNT-aerogel as electrodes and P(VDF-HFP)/EMIMBF4 ionogel as electrolyte.The introduction of the ionogel electrolyte increases the operating voltage of the FSC to 3V.and makes the device combine the intrinsic high power density(27.3 kW kg-1)of non-faradaic SCs with an ultrahigh energy density of 29.6 Wh kg-1.which has reached the level of lithium-ionbatteries.More importantly,the assembled FSCs show excellent flexibility and bending-stability,and can still operate normally within a wide working temperature window(0?80?).The outstanding electrochemical performance and the mechanical/thermal stability indicate the assembled FSC device is a promising power source for flexible electronics.