Preparation Of Carbon Based Materials Loaded With NiFe Prussian Blue For Capacitive Properties

In recent years,in order to solve the problem of low energy density of supercapacitors,battery-type materials have been introduced to overcome the problem of energy density.Even though,battery-type materials suffer from the tortures of low rate capability and inferior cycle life,which concers limit the further development of these materials in the field of capacitors.How to maintain high energy density and good rate performance is still one of the most challenging problems.In this paper,NiFe Prussian blue analogue(NiFePBA),a typical battery-type material,was used as the basic building unit with using carbonized bacterial cellulose nanofibers and reduced graphene oxide(rGO)as the conductive matrix to praper a series of composites.The energy density and scaling performance were successfully improved through different technical paths,offering some meaningful experience for the later exploration.The specific work is as follows:(1)Although prussian blue and its analogs have many excellent electrochemical features such as good ion storage performance,low cost and simple preparation methods,their poor electrical conductivity and inappropriate rate performance limit their application as electrode materials for supercapacitors.Three-dimensional carbon nanofibers derived from bacterial cellulose prepared by carbonization of the large-scale production of bacterial cellulose were used as the conductive matrix after cladding polyaniline(PANI).Then NiFePBA was grown in situ under mild conditions that were easy to industrialize.Finally,the complex carbonizing BC/PANI/NiFePBA was prepared.Its specific capacitance of 425 F g-1 is higher than that reported in the literature.Continuous charge and discharge(current density:1 A g-1)can maintain 80%of the initial capacitance after 2000 cycles,and has A good rate performance.The effects of polyaniline polymerization time for the electrochemical properties was investigated and the best reaction time was determined.(2)Graphene has been industrially produced and has been widely used in the electrode materials of supercapacitors as an active electrode material or conductive substrate.NiFePBA was grown in situ by reducing graphene oxide(rGO)as the conductive matrix.The structure and crystal size of NiFePBA were regulated by changing the concentration,additive and reaction time of the precursor,so as to improve the capacitance and ratio of the composite.At the same time,the effect of reduction degree of rGO on the overall properties of the material was also explored,and the optimal reduction conditions were determined,and the optimal reduction conditions were determined.The specific capacitance of the composite rGO2/NiFePBA7 is 546 F g-1(current density is 1 A g-1).When the current density is increased by 5 times,the specific capacity can be maintained to 87%.Finally,by growing NiFePBA nanoparticles on polyaniline-coated rGO2 nanosheets,the cycling stability was improved from 57%of the original rGO2/NiFePBA7(2000 cycles)to 78%of rGO2/PANI/NiFePBA compound.