Application Of Cellulose Nanomaterials In Composite Conductive Aerogels

With the gradual development of scientific and technological power in the world,energy demand has gradually become a huge part of the needs of people all over the world.Supercapacitors are becoming more and more dazzling in the field of energy storage materials research because of their excellent electrochemical performance and long cycle life.Graphene is often developed and used as conductive active material because of its strong electrical conductivity and huge specific surface area.Polypyrrole as a conductive polymer can provide better specific capacitance than graphene.The supercapacitor electrode material with the combination of polypyrrole and graphene has the advantages of high conductivity,high specific capacitance and long cycle life.However,the material has the disadvantage that the structure is easy to agglomerate,which leads to the decline of electrochemical properties.Cellulose has an excellent dispersion effect on conductive active materials,and the cellulose nanomaterials prepared from fibers include cellulose nanofibers（CNF）and cellulose nanocrystals（CNCs）.After cross-linking,porous network structures can be formed by freeze-drying.The structure provides the function of dispersion,support and attachment for electrically active materials.Therefore,it is expected to prepare supercapacitor electrode materials with high electrochemical performance by combining graphene and conductive polymers based on nanofiber materials.In order to explore the advantages and disadvantages of cellulose nanomaterials prepared by CNF and CNCs for the electrochemical performance of composite energy storage electrode materials,on the basis of cellulose nanofibers（CNF）prepared by TEMPO oxidation,polypyrrole（PPy）was prepared with Fe Cl3·6H2O as oxidant,graphene oxide（GO）was introduced,and aerogels were prepared by freeze-drying method.Then,Graphene oxide which was well dispersed in the system was reduced to reduced graphene oxide（RGO）by vitamin C.Finally,CNF/RGO/PPy composite aerogel was obtained,which has the advantages of three-dimensional network structure,high porosity,low density,high specific surface area and excellent electrochemical performance.Another new aerogel electrode material was prepared by combining RGO and PPy in the form of physical cross-linking of CNCs.The two kinds of aerogels were characterized and analyzed,and the effects of different composite ratios and preparation methods on the mechanical and electrochemical properties of aerogels were discussed.Because the composite aerogel has rich pore structure to form pores,which is conducive to electron transport efficiency and electrolyte penetration,has natural advantages and great potential for the application in the field of new energy storage electrode materials.The contents of the study are as follows.1.In the case of only introducing GO,the morphological structure and electrical conductivity of aerogels with different amounts of GO were investigated.The structure shows that the conductivity was 5.21 S/cm when CNF/GO is 3:1,and the structure was compact.When the proportion of GO continued to increase,the conductivity increased slowly,but the structure appeared the phenomenon of loose collapse,so the proportion of3:1 was selected for the follow-up experiment of introducing polypyrrole.2.When introducing PPy,the effects of mechanical mixing and in-situ polymerization on the electrochemical properties of the composites were investigated,and the effects of different composite ratios were discussed.The results show that the in-situ polymerization method has better pore structure and electrochemical performance than the mechanical mixing method,and the electrochemical performance is the best when CNF:RGO:PPy=6:2:3 is used.When the current density is 0.25m A cm-²,the specific capacitance is 327.2 F·g^-1.3.After the energy storage electrode materials were prepared from two different cellulose nanomaterials,the structures and properties of the two materials were compared.The results show that the composite conductive aerogel based on CNCS physically crosslinked PVA has more significant advantages in electrochemical performance,and the compression performance of the material is also better.When the current density is 0.25m A cm^-2,the specific capacitance is 352.2 F·g^-1.