Self-stretchable Supercapacitors Based On Carbon Nanotube/Ploypyrrole Fibers

Carbon nanotube(CNT)fiber is widely used in sensors,energy materials,and flexible wearable devices because of its excellent mechanical properties,electrical properties and thermal conductivity.Lightweight,flexible fiber supercapacitors have been paid more and more attention by researchers.However,most of the fiber supercapacitors are fabricated by wrapping two straight fibers together,the tensile propertie is restricted because of its own small stretch strain and low elasticity characteristics.In order to allow the supercapacitor to work stably under complex deformation conditions such as bending,stretching,etc.,the researchers fabricate a stretchable fiber-shaped supercapacitor by attaching the active materials to the elastic polymeric substrates.In this paper,a self-stretchable carbon nanotube composite fiber supercapacitor is fabricated by using its own spiral ring structure.In this thesis,carbon nanotubes / polypyrrole(CNT/PPy)composite films whose area can be up to 4cm*12cm are fabricated by chemical in situ polymerization.CNT/PPy composite fibers and helical fibers are prepared by traditional spinning process.The problem that the pseudocapacitive materials are mostly loaded on the fiber surface of carbon nanotube composite fibers,limiting its capacitive properties is solved.It is found that polypyrrole loaded on carbon nanotube bundles doesn't fall off during spinning.When the volume ratio of pyrrole / ethanol is 3:300,the specific capacitance of CNT/PPy composite fibers electrode reaches 261.3 F/g.The two CNT/PPy composite fibers are assembled into fiber-shaped supercapacitor and the capacitance performance is studied.The specific capacitance of composite fibers is 196.2 F/g at 5 mV/s,and after 2000 times of galvanostatic charging and discharging,the CNT/PPy composite fiber shows a capacitance retention of 70%.The capacitance stability of CNT/PPy composite fiber should be further enhanced.The CNT/PPy helical fibers are used to prepare the all-solid and self-stretchable supercapacitor and their capacitance performance is studied.The specific capacitance of the composite helical fiber supercapacitor is 166.1 F/g,and the mass specific capacitance retention rate is 60% after 1000 charging-discharging cycles.Since the CNT/PPy helical fibers themselves have good flexibility and stretchability,the capacitance performance is stable at 80% tensile strain and bending deformation.By introducing metal oxide material manganese oxide(MnO2),the carbon nanotubes/manganese oxide(CNT/MnO2)composite fibers are fabricated and show a specific capacitance up to 158.8 F/g.In order to further improve the capacitance performance of CNT/PPy composite fibers,carbon nanotubes/polypyrrole/manganese oxide(CNT/MnO2/PPy)ternary composite fibers are fabricated and find that the specific capacitance and capacitance cycling stability of ternary composite fibers are higher than that of binary composite fibers.After 2000 charging-discharging cycles,the mass specific capacitance retention rate can reach 85%.