Preparation,characterization Of Nitrogen-doped Porous Carbon-based Nanomaterials And Energy Storage Properties Of Supercapacitors

Electrochemical supercapacitor?supercapacitor?is a new energy storage technology,having outstanding characteristics of high power density,long cycle life and fast charging speed,and will play a key role in the future energy storage field.At present,the development of supercapacitors is mainly limited by relatively low energy storage density.As the core component of supercapacitors,electrode material is one of the main factors affecting the energy storage density of supercapacitors.Therefore,the development of high-performance electrode materials has become a research hotspot.Carbon materials have good conductivity and high specific surface area,which are often used as matrix materials and electrode materials of supercapacitors.For carbon based electrode materials,the capacitance performance usually depends on the surface area,surface activity and porosity of carbon materials.However,there are few active sites on the surface of carbon material,which lead to the reduction of effective area of electric double layer,thus making its potential capacitance performance difficult to reflect.Especially for powdered carbon materials,the addition of binder during electrode preparation not only further reduces the contact surface area of the active material and the solution,but also limits the rapid transfer/migration of electrons and ions during the charge-discharge process.In view of the above problems,it is very important to develop the active carbon based electrode materials with self-supporting characteristics,that is,to build ultra-long continuous,three-dimensional conductive network,as well as the electrode materials with interconnected,three-dimensional porous structure characteristics,so as to ensure the continuous and rapid transmission of electrons and ions.This work focuses on the research of multi-template growth of polyaniline to prepare nitrogen-doped three-dimensional porous carbon-based electrode and its surface activity regulation,porous structure regulation,self-supporting,three-dimensional continuous structure,etc.The main achievements are as follows:?1?Electrospun PAN nanofibers were used as the substrates.Through in-situ chemical polymerization of aniline monomers,flexible PAN@PANI core-shell composite nanofibers were prepared.After high temperature carbonization,the self-supporting NPCNFs composites were obtained.The deposited PANI not only serves as a porous template and pyrolyze at high temperatures to form interconnected ordered porosity,but also provides a nitrogen-rich source for in-situ nitrogen doping.Under the three-electrode test,when the current density is 0.5 A/g,the NPCNFs electrode has a high specific capacitance of 130 F/g,which is twice that of pure CNFs.This excellent performance is attribute to the doping of the nitrogen atoms which forms a porous structure,increases the specific surface area,and provides pseudocapacitance,finally effectively improves the electrochemical performance.In addition,in order to further improve the capacitance,we synthesized NPCNFs/PANI composites and assembled into all-solid-state flexible symmetric supercapacitor.Thanks to well-designed structure,the device achieves a high specific capacitance of260 F/g at a current density of 0.5 A/g.At the same time,the device can provide a high energy density of 8.9 Wh/kg at a power density of 0.27 k W/kg and excellent cycling stability with 80.1%capacitance retention after 10,000 charge-discharge.?2?Self-supporting porous carbon materials with advantages such as high specific surface area,ordered porosity,and continuous conductive paths show ideal charge storage capabilities in supercapacitors.Natural structures can provide ideal models to develop a variety of bionic buildings.The natural ant nest has a three-dimensional staggered open frame structure,which is very conducive to the rapid transport of ions and electrons.Inspired by the ant nest structure,we used the phase separation principle to immerse the PAN/PVP/DMF ternary solution system in water to remove PVP and DMF to construct a porous PAN film material.Then,using PAN film material as template,after in-situ chemical polymerization of aniline monomer and high temperature carbonization,self-supporting nitrogen doped hierarchical porous carbon film material?NHPC?with a highly cross-linked skeleton structure and high specific surface area was prepared,as the negative electrode of the supercapacitor.Generally,asymmetric electrodes can widen the potential window of supercapacitors and thus increase energy density.Therefore,in order to match the negative electrode,we designed the HPC/Mn O₂ positive electrode material based on HPC,and assembled into button-type asymmetric supercapacitor.Electrochemical performance tests show that the stable potential window of the device can be as high as 1.6 V,with a high specific capacitance of 253 F/g at a current density of 0.5 A/g.And when the power density is 410 W/kg,a high energy density storage of 21 Wh/kg is achieved,which shows excellent electrochemical performance.