Preparation,Characterization And Properties Of Fiber-shaped Asymmetric Supercapacitors

With the development of flexible wearable electronic devices,various portable electronic products have emerged into modern society.Smart bracelet,health monitor and other electronic devices have facilitated people's life.Compared with planar flexible devices,fiber-shaped wearable electronic devices embrace many advantages such as light weight,small volume and easy to carry.As one of the fiber-shaped flexible wearable electronic devices,fiber-shaped energy storage devices have been executed in society.Compared with the fiber-shaped battery,the fiber-shaped supercapacitors have the advantages of high power density,ultrafast charge/discharge capability,excellent cycle stability,large operating temperature window,good safety performance,easy knitting and cutting,etc..Therefore,it is expected to become a new generation of energy storage device.However,low energy density limits the development of the fiber-shaped supercapacitors in practical applications.Therefore,researchers expect to improve the energy density of the device without reducing their power density.Developing a fiber-shaped asymmetric structure is an effective way to improve the energy density of a fiber-shaped supercapacitor?FASCs?device by widening the working voltage of the device and increasing the specific capacity of the device.In addition,in order to effectively meet the development requirements of miniaturization and integration of flexible wearable electronic devices,FASCs with advantages of tiny volume,light weight and knitting provide a new idea for the development of new energy storage devices.Thus,in this thesis,we mainly focus our research on developing highly capacitive electrode active materials and designing new device structures to fabricate FASCs with high energy density,and integrated them to obtain self-powered charging system and self-energy monitoring system.The main research contexts are summarized as follows:?1?Fe-Co-Ni ternary oxide?FCNO?nanowire arrays?NWAs?are directly grown on graphene fiber?GF?with a facile and effective hydrothermal approach.FCNO NWAs composite fiber electrode delivers an impressive specific capacitance of 1.34 F cm^-2 at a current density of 0.5 mA/cm².We successfully fabricated high-performance ASCs with a maximum operating voltage of 1.4 V by adopting FCNO NWAs/GF as the positive electrode and CNR/GF as the negative electrode.The as-fabricated asymmetric device exhibits a high specific capacitance and energy density.In addition,the as-prepared device embraces the excellent cyclic stability.Meanwhile,the as-fabricated FASCs device are woven into flexible energy textile with conventional weaving techniques.?2?A series of novel fiber-shaped composite electrodes are prepared by a facile chemical method and subsequent annealing process.As the as-prepared electrode material possesses the unique hierarchical and porous structure,which can provide abundant active sites and facile ion diffusion path,and the assembled FASCs device embraces excellent electrochemical performance.Additionally,a self-charging power system is fabricated,which is composed of FASCs and flexible triboelectric nanogenerator.?3?MnO₂ nanoballs@Ni cone three-dimensional hierarchical structure are directly grown on carbon nanotube?CNT?film with a facile secondary electrochemical deposition process.We successfully fabricated a prototype coaxial FASCs with a maximum operating voltage of 1.8 V by adopting a MnO₂nanoballs@Ni cone as the core electrode and MoS₂ NSAs/CNTFs as the outer electrode.The as-assembled coaxial FASCs embraces a remarkable specific capacitance due to the synergistic effect between positive and negative material.Furthermore,the as-fabricated device also embraces excellent cycle life in that its capacitance retention reaches 88.4%after 6 000 cycle tests.Moreover,the capacitance retention can still reach 96.9%after 4 000 bending cycles,showing excellent mechanical flexibility and stability.Additionally,we have successfully prepared a novel FASCs/humidity sensor integrated device,which can simultaneous realize energy storage and environmental humidity monitoring.?4?We have successfully fabricated V₂O₅ and VN hollow fibers positive and negative electrode substance by a facile electrospinning method and annealing process.Meantime,V₂O₅/SWCNTS composite fiber,VN/SWCNTs composite fiber and rGO based temperature sensor are obtained by 3D printing technology.We successfully fabricated high-performance FASCs with a maximum operating voltage of 1.6 V by adopting V₂O₅/SWCNTS composite fiber as the positive electrode and VN/SWCNTs composite fiber as the negative electrode.The as-fabricated FASCs delivers an impressive specific capacitance of 116.19 mF cm^-2 at a current density of 0.6 mA/cm².In addition,the assembled device embraces the excellent mechanical flexibility and stability.More importantly,rGO fiber based temperature sensor can be integrated with3D printing FASCs device as the external power source,the temperature sensitive of integrated device is 1.95%/?.