Preparation And Capacitive Properties Of Electrode Materials For Flexible Supercapacitors

Research and preparation of flexible energy-storage device and elastic conductor are motive force for development of flexible/wearable electronic equipment.Among flexible energy-storage devices,flexible supercapacitor has shown a promising application prospect due to favorable energy store property,mechanical flexibility and operational reliability.In the recent years,remarkable progress has been made in flexible supercapacitor and elastic conductor.However,there are still some shortcomings such as low material utilization,poor stability,and specific capacity degradation especially at high charge-discharge rate in flexible supercapacitor.For elastic conductor,the high cost,poor adhesion between conductors and elastic matrix is still exists,and conductive mechanism of wrinkle-structure conductor under stretching remains unclear.In this dissertation,the utility and mechanical stability of electrode materials have been optimized through structural design and their composite with carbon nanomaterials.The relation between rate performance and electrode resistance has been studied by compressible electrode resistance variation properties.The conductivity mechanism for stretching elastic conductor has also been analyzed based on a wrinkle-structure elastic conductor on elastic matrix using simple chemical polymerization method.The corresponding significant results as follows.?1?The vertical polypyrrole nanotubes?VPPyNTs?on underlying PPy granule?PPyG?film as electrodes were grown by a facile self-degraded template method through a one-step chemical oxidation process.In the hybrid electrode?VPPyNTs/PPyG?,the vertical PPy nanotubes can not only improve the surface area of electrode materials,but also the transport speed of ions and electrons.The specific capacity of the hybrid electrode was about 1.6 times comparing to PPyG film.The corresponding mechanical stability was improved by compounding the electrode with carbon nano onions?CNOs??VPPyNTs/CNOs@PPyG?.The spherical-structured CNOs can relieve stress concentration in PPyG film during stretching,and maintain conductivity of the electrode.The charge-discharge cycle stability was also improved by CNOs.The flexible supercapacitor based on VPPyNTs/CNOs@PPyG electrode has a high specific capacity(64 F g^-1)and outstanding tensile properties?capacitance retention of 99%after 500 cycles?.This flexible supercapacitor can maintain stable energy output under bend or fold states.This wearable supercapacitor based on PPy-nanostructred textile offers a novel approach for designing flexible electrode devices.?2?A multi-walled carbon nanotube/MnO₂@multi-walled carbon nanotube?MWCNT/MnO₂@MWCNT?composite as a compressible electrode was prepared within sponge matrix.The charge-discharge current density and the rate capability are improved along with the increase of compression ratio.The current density is about 7 times under compression comparing to uncompressed electrode at the same specific capacitance,and the capacity retention increase to 55%from 16%.The internal resistance was decreased due to the reduction of resistance under compression,and the transmission performance of ions and electrons was enhanced own to the reduction of electrode polarization,giving a high current charge-discharge and rate capability.?3?A wrinkle-textured polypyrrole-latex?PPy-Latex?elastic conductor was grown on latex fiber.The as-prepared PPy-Latex has good adhesion,excellent conductive stability,and mechanical stability.The PPy-Latex can retain the electrical conductivity even under a strain of 400%?the ratio of relative resistance is only 1.3?.After 500 stretching cycles at a strain of50%,it still presents an excellent mechanical stability with a relative-resistance ratio of about1.5.The wrinkle structure can protect elastic conductor by releasing internal expansion space,and has the ability to adjusting conductive pathway.Its high wrinkle-density can provide large internal expansion space and ample conducting-pathway during stretching,which is suitable for large stretch.This study offers a strategy for the development of novel wrinkle-textured conductors.