Synthesis And Characterization Of Fiber-shaped Electrochemical Energy Storage Device

Fiber-shaped flexible devices featured many advantages such as being lightweight,wearable and integrated,has become an important research topic in the field of wearable electronics.As the core component of fiber-shaped devices,fiber-shaped electrodes have received intensive attention.As known,metal wires and yarns are the typical fiber-shaped materials,however,their functionalization towards fiber-shaped electrodes is still a great challenge.This thesis has extended 3D CNT-graphene structure,a type of promising electrodes developed by our group previously,to grow on metal wire/tube current collectors.These prepared CNT-graphene wire and tubular electrodes allow the preparation of coaxial-cable supercapacitor.Besides,the 3D CNT-graphene electrodes were used as the substrate to support porous carbon and transition metal sulfide nanosheets for high-performance asymmetric supercapacitors.Based on the structural characteristics of the yarns,a capillary dyeing approach has been developed to fabricate an air electrode by inhibibiting active material ink into conductive metal/cotton yarns.Then a flexible fiber-shaped lithium-oxygen battery was assembled.The main research contents are as follows:1.An all-inclusive fully functional supercapacitor.More specifically,CNTs and graphene are grown on Ni wires and in Ni tubes by two-step chemical vapor deposition(CVD)process.Then Mn O2 nanosheets are deposited onto CNTs.The Ni wires and tubes decorated with Mn O2-CNT-graphene hybrids are used as inner and outer electrodes to assemble cable-structure supercapacitors.This supercapacitor exhibits a large areal capacitance at the current density of 0.29 m A cm-2 and the corresponding areal energy density and power density are 2.76 ?Wh cm-2 and 230 ?W cm-2,respectively.And the capacitance retention of the supercapacitor is ~82% after 10000 cycles at the current density of 0.38 m A cm-2,indicating an excellent cycling stability.2.High-performance asymmetric supercapacitor.Nitrogen-doped CNT(NCNT)-graphene hybrids are prepared as current collectors for asymmetric supercapacitors.Here,Ni Co2S4 nanosheets and MOFs are in-situ grown on the surface of the NCNTs with the assistance of electron-riched N dopants.The MOFs-derived porous carbon/NCNT-graphene composites are used as negative electrodes and Ni Co2S4/NCNT-graphene composites used as positive electrodes.This asymmetric supercapacitor showed a high specific capacitance of 240 F g-1 at the current density of 2 A g-1.3.High-performance flexible lithium-oxygen(Li-O2)battery.Ru O2-coated nitrogen-doped CNTs(Ru O2/N-CNTs)ink is dyed to the surface and pores of metal wire/cotton fiber yarns via the intrinsic capillary of yarns,forming a freestanding air electrode that used to assemble wire-shaped Li-O2 battery.The assembled wire-shaped Li-O2 battery delivered a discharge capacity of 1981 m A h gcarbon-1 at a current density of 320 m A gcarbon-1.The battery can be fully recovered and can work for 100 cycles(>600 h)without obvious degradation even under bending conditions,demonstratin outstanding flexibility and stability.