Study Of Self-supporting Flexible Electrodes Based On Polyporrle/pure Cotton For All-solid-supercapacitors

In modern society,as intelligent wearable devices are widely used in healthy care,military communications and other fields,the gradually increasing demand for energy,the energy transfer and storage system requirements are also environmentally friendly,cheap and flexible folding,developing a new generation of energy storage devices become one of the challenges to the modern science and technology development.As a common energy storage device,supercapacitor has the advantage with long cycle life,environmental friendly and high charge-discharge efficiency,but the traditional capacitor rigidity is not suitable for application in the field of flexible wearable,so the flexible supercapacitor become the hot research pot.Cotton is an ideal clothing material with good performance and low price,polypyrrole（PPy）is easily synthesed and environmental friendly.The PPy/Cotton fabric become one of the extremely potential application electrode materials for flexible energy storage device,but the low conductivity,poor circulation stability become the bottleneck problems in the development.In addition,through controlling the temperature of the heat treatment,the non-conducting cotton fabric can transfer to electrical conductivity and retain the original carbon fabric weave structure,by using the rich nitrogen source of the PPy molecule,the research of PPy/Cotton based carbon fabric open a new path to improve the energy storage performance of textile fiber in flexible electrode.The main research contents of this paper are as follows:Preparation of PPy@CNTs/Cotton electrode and the performance of solid-state supercapacitor.The PPy@CNTs/Cotton fabric electrode was synthesied through a facile dipping-oxidative in-situ polymerization method.The mechanism of PPy@CNTs composite uniformly deposited on the surface of Cotton fabric was discussed and the flexible all solid supercapacitor（FL-SCs-1）was assembled by using PVA/H₃PO₄ electrolyte.The transmission electron microscopy（TEM）showed that PPy was evenly covered on the surface of CNTs and the thickness is approximately 34nm.FL-SCs-1 test results indicated that the voltage window is 0-0.8V and the specific capacitance of the FL-SCs-1 is 206.8 F/g at a current density of 1 mA/cm²,the energy density is 19.6 Wh/kg and the capacitance retention is 72%after 400 times charge and discharge cycles.Preparation of polyprrrole/pure cotton nitrogen-doped carbon fabric（N-CT）electrode and the performance of the solid-state supercapacitors.Using pure cotton fabric as the substrate to prepare PPy/Cotton composite,the N-CT electrode was obtained by high temperature carbonization and PVA/LiCl was used as the neutral electrolyte to assemble the FL-SCs-2.The results showed that when the concentration of Py monomer was 1.2 M,the PPy/Cotton fabric was calcined at 900 ^oC for 3 h at a rate of 5 ^oC in N₂ atmosphere,the sheet resistance of N-CT electrode was 7.8±1.9Ωwith good flexibility and mechanical strength.The X-ray electron spectroscopy（XPS）shown that the nitrogen content of N-CT electrode material was 2.24%.The electrochemical test showed that the specific capacitance of 256.2 F/g was obtained at charge-discharge curves at a current density of 0.5 A/g,the capacitance retention was98.3%after 5000 charge-discharge cycles and the coulomibic efficiency was about98.8%at the whole charge-discharge cycle.The results of FL-SCs-2 test showed that the voltage window of the FL-SCs-2 can reach 0-1.6 V,the capacitance was 124.9 F/g at a current density of 2 mA/cm² and the energy density is 28.6 Wh/kg.The capacitance retention is 93.8%after 1000 charge-discharge cycles and the coulomibic efficiency was about 98%at the whole charge-discharge cycle.Due to its several favorable traits such as flexibility,excellent electrochemical cycleability,it has potential application value in the field of wearable energy storage.Preparation of polyprrrole/pure cotton based iron oxide/nitrogen-doped carbon composite fabric（Fe₂O₃/N-CT）electrode and the performance of solid-state supercapacitors.The pure cotton fabric was used as the substrate to prepare PPy/Cotton fabric,Fe₂O₃/N-CT was prepared by in-situ polymerazation-high-temperature calcining method and PVA/LiCl neutral electrolyte was used to assemble FL-SCs-3.X-ray diffraction（XRD）,X-ray electron energy spectrum（XPS）and Field emission scanning electron microscope（FE-SEM）shown that the main composition of Fe₂O₃ wasα-Fe₂O₃ andγ-Fe₂O₃ and the surface of N-CT was covered by nanoscale sheet-shape grains Fe₂O₃.The electrochemical test showed that the Fe₂O₃/N-CT electrode had a specific capacitance of 429.6 F/g at a current density of0.5 A/g,it’s 1.6 times of N-CT,and the capacitance retention was 93.4%after 3000charge-discharge cycles.FL-SCs-3 test indicated that the voltage window can reach0-1.8 V,its benefit the use of porous materials,mixed atoms and neutral electrolytes.The capacitance retention was 88.4%after 1000 charge-discharge cycles and the coulomibic efficiency was about 92.3%at the whole charge-discharge cycle.The energy density is 61.2 Wh/kg,which is 2.1 times of based on N-CT supercapacitors.This research shown excellent energy storage performance and has a good prospect in the field of flexible supercapacitor.