Construction And Performance Of Flexible Supercapacitors Based On Carbon Nanotubes Macroscopic Film

With the exponential development of science and technology,intelligent portable and wearable electronic devices have appeared in various fields.Supercapacitors are a promising candidate as power supply for smart portable intelligent electronic devices due to their high power density,fast charging process,long service life and safety.Flexible supercapacitors have attracted extensive interest and research to fulfill the requirements of flexibility and miniaturization aroused from portable and wearable electronics.Flexible two-dimensional?2D?tandem supercapacitors and one-dimensional?1D?fiber supercapacitors have been successfully developed and a great progress has been gained.However,there are still some disadvantages such as low volumetric specific capacitance and energy density,poor stability,and specific capacity degradation especially under dynamic deformation.this thesis focuses attempts to design novel structured devices,and simplify the fabrication process.The corresponding significant content and results as follows:?1?Supercapacitors based on metallic collectors possess an interface imperfection,causing long ion diffusion pathway and hindered electron conduction,as well as inferior flexibility.Herein,we explored carbon nanotubes macroscopic film?CMF?as current collectors to build desired electrodes with connection structure via anchored combination between CMF and commercial active carbon?AC?.In addition,the CMF presented outstanding electroly tepermeation,which increases the electron conduction,shortens the ion diffusion pathway and ameliorates the flexibility.Compared with that with metallic collector,the supercapacitor based on CMF exhibites prominent electrochemical performances of specific capacitance?48.5 F/cm³ at 0.1 A/g?,rate capability?82.5%from 0.1 to 16 A/g?and volumetric energy density?104.9 Wh/L?,More importantly,the supercapacitor exhibits remarkable stability under different folding conditions,even under low temperature and pressure.Therefore,it is believed that this supercapacitor based on CMF is promising in future wearable energy storage devicesin different operating environments,as well this strategy based on interface engineering will open up a brand new perspective to prepare high-energy-density materials for the requirement of electronic devices.?2?One-dimensional?1D?power storage devices with impressive flexibility and stitchability are promising in facilitating devices assembly and provide highly efficient power sources for wearable electronics.Current 1D devices are suffered by relatively low loading mass and limited surface area which leads to unsatisfied electrochemical properties and is difficult to meet the energy density demand.In this research,we employed CMF as current film to loading active materials(Li₄Ti₅O₁₂ as anode and active carbon as cathode)for fabricating 1D cable-type lithium-ion supercapacitors?CLiSc?.Active materials were anchored on the surface of CMF and the electrodes were coupling on the surface of carbon nanotubes?CNTs?As results,the electrodes achieved a high loading mass of 13.6 mg/cm²,and the obtained CLiSc exhibited high capacity and excellent durability,especially the satisfactory volumetric energy density of 14.1 mWh/cm³,which surpassing the previously reported supercapacitors?approximately 5 times?.Moreover,the fiber devices remain more than 87.4%of initial capacitance?42.1 mAh/g at 1 A/g?after 3500 bending cycles,showing very stable mechanical stability.These were attributed to the anchored effect and large contact area of electrodes delivering rapid electronic/ionic transport kinetics.Furthermore,the CLiSc can be normally powered in various kinds of actual service conditions,such as bent,knot,weave and serial and parallel integration.In addition,the CLiSc could be expediently connected with electronics in the same side by the carbon nanotubes fiber?CNF?.This novel CLiSc is expected to be used in wearable electronic devices.