The Construction Of Three-Dimensional Structure Of Conductive Polypyrrole/Metal Organic Framework Composites And Their Application On Supercapacitors

Supercapacitors have the outstanding features of higher power density,longer cycle life and lower cost,which are ideal power supply devices for a new generation of miniaturized,wearable,intelligent and flexible electronic equipment.Metal-organic frameworks(MOFs)have become new electrode materials for flexible wearable supercapacitors owing to their excellent characteristics of porous structure,large specific surface area,rich active sites,adjustable structure,etc.However,the inherent conductivity of most MOFs is poor,resulting in low capacitance.A small number of MOFs with high conductivity are also restricted to the type,preparation conditions,yield,and development cost.In addition,using MOFs as sacrificial templates to prepare electrode materials such as porous carbon or metal oxides is easy to cause structural collapse and reduce specific surface area.In order to solve the bottleneck,hybridizing MOFs with other conductive materials is an effective strategy to give MOFs high conductivity and improve the capacitance performance without sacrificing the advantage of high specific surface area of MOFs.Conductive polypyrrole(PPy)has the advantages of good conductivity,low cost,easy synthesis and so on.Therefore,this thesis conducts related research on the preparation of PPy and MOFs composite materials,and their application on flexible all-solid-state supercapacitors.The main research contents include:1.Cu₃(2,3,6,7,10,11-hexahydroxytriphenylene)₂ MOF(Cu-CAT)and porous polypyrrole(p-PPy)composite electrode materials were prepared by solvothermal method.Cu-CAT has a certain electrical conductivity,and is deposited onto the inside and outside of p-PPy with the structure of nanorods-aggregated nanoparticles.The three-dimensional porous structure of p-PPy helps the electrolyte to diffuse,achieves good mass transfer and more diversified electron transmission paths.What's more,p-PPy provides sufficient loading sites and effective conductive skeleton for Cu-CAT.The flexible all-solid-state supercapacitor based on the composite material has achieved a specific capacitance of 233 m F cm^-2,a maximum power density of 1.5 m W cm^-2,a maximum energy density of 12?Wh cm^-2,and the capacitance retention of more than 85%after more than 5000 cycles of charge/discharge.At the same time,the device shows a wide operating temperature range and good mechanical flexibility.2.In the previous part of the work,the p-PPy/Cu-CAT composite material was in a block shape.When preparing the flexible electrode,carbon cloth was used as the substrate and a binder was required.At the same time,Cu-CAT was a structure of nanorods-aggregated nanoparticles,which was easy to agglomerate and was not conducive to the diffusion of electrolyte.In this work,a two-step method of electrodeposition and solvothermal was adopted to realize the large-scale preparation of PPy hollow foam supported Ni-MOF nanowire composites.The skeleton of PPy foam was the hollow structure,and the Ni-MOF nanowires were synthesised onto the surface and inside of the skeleton,achieving the high load of Ni-MOF.The ordered Ni-MOF nanowire arrays provide certain electrical conductivity and high specific surface area,while the three-dimensional porous network of flexible PPy hollow foam is conducive to rapid ion diffusion and efficient electron transport.This composite material can be directly used as a flexible electrode without any substrate,conductive agent and binder,and the specific capacitance of the electrode is as high as 1050 m F cm^-2.The flexible all-solid-state supercapacitor based on PPy HF/Ni-MOF-NWs has excellent electrochemical performance,good cycling stability,temperature resistance,mechanical flexibility and a wide operating temperature range.The device can be made into a watchband to drive an electronic watch,which has the potential of the application in wearable devices.