Electrochemical Properties Of Cellulose Network/Polyaniline Composites

The excessive consumption of fossil fuels and the accompanying environmental pollution force countries to seek renewable and sustainable new energy sources and green and efficient energy storage technologies.As one of the most important energy storage devices,supercapacitors have the advantages of high power density,fast charging,long cycle life and good security.To further meet the needs of the green and sustainable development of supercapacitor energy storage materials,the development of biomass based energy storage materials and supercapacitors has become a research hotspot.Among them,wood is rich in reserves,renewable and has the hierarchical porous structure.The preparation of energy storage materials and supercapacitors based on it will provide a new possibility for the sustainable development of the energy storage field.In this paper,a variety of wood cellulose network/polyaniline composite materials were prepared by in situ polymerization,vacuum impregnation and electrochemical deposition of polyaniline and carbon nanotubes,polyacrylamide and others in the hierarchical porous structure of the cellulose network,and their electrochemical properties were studied.The main research contents and conclusions of this paper are as follows:(1)Cellulose network/polyaniline composites with high electrical conductivity(36.79 S/cm)can be obtained through chemical purification of wood to obtain the cellulose network structure retaining the original structure and in situ polymerization and deposition of polyaniline.The supercapacitor assembled with it showed good electrochemical performance,and the area ratio capacitance can reach 0.12 F/cm~2 at the scanning rate of 5 mV/s.The porous structure of cellulose network provided sufficient space for in-situ polymerization of aniline,which endowed the material with extremely high polyaniline load.At the same time,a large amount of polyaniline was fixed in the cellulose structure through hydrogen bonding,which effectively improved the electrical conductivity of the composite material and made the assembled supercapacitor have good electrochemical properties.(2)Multiwall carbon nanotubes/cellulose network/polyaniline composite material with layered structure was prepared by vacuum impregnating carbon nanotubes into the wood cellulose network and in situ polymerizing and depositing polyaniline.The all-solid flexible supercapacitor can be assembled by combining the gel electrolyte with the composites.The regulation of polyaniline polymerization conditions can result in a sandwich structure of"conductive layer-diaphragm-conductive layer"of the composites,which enabled the construction of the all-in-one flexible supercapacitor.The assemblyed supercapacitor has exhibited excellent electrochemical performance with a specific areal capacitance of 0.71 F/cm~2 at the scan rate of 2 mV/s and a retention rate of specific capacitance of 103.24%after 10000 cycles under the current density of 3 A/g.At the same time,it has good flexibility.When the bending angle was 180°,the capacitance retention rate was up to 80.95%.The abundant pore structure of cellulose network enabled the device to realize a great mass loading of active substances,and the combination with electrolyte gave the device excellent flexibility.The integrated structure reduced the contact resistance and distance between the layers,promoted the fast ion transmission,and realized the efficient electrochemical energy storage of the device.(3)Acrylamide and lithium chloride were compounded in the matrix of cellulose network by means of vacuum impregnation,conductive composite hydrogel was formed through in situ polymerization of acrylamide,polyaniline was synthesized by electrodeposition on the surface of the hydrogel,and then transparent,conductive,electrochromismcellulose network/polyacrylamide/polyaniline composites with the construction of sandwich was obtained.And electrochromism supercapacitor can be assembled based on the composites.The device showed good performance of electrochemical(potential window can reach 1.6 V),the obvious color change(transmittance difference of 9.66%).The excellent conduction of lithium ion and the effective electrodeposition of polyaniline on the surface of the hydrogel gave good electrochemical performance and electrochromic ability of the composites.