Synthesis Of Porous Carbon Nanospheres And Application In Supercapacitor

Supercapacitors（SCs）,as a new type of energy storage device,store the energy by ion adsorption.It can realize fast energy storage within a short time（<10 s）,achieve long cycling life（up to 10⁵cycles）and ultrahigh power density(>10 kW kg^-1)far exceeding that of batteries.However,the pervasive application of current supercapacitors have still been constrained by its relatively low energy density(～5 Wh kg^-1)compared with lithium ion batteries.In order to develop a supercapacitor with a high energy density,electrode materials with excellent energy storage properties should be developed in the first place.Among all the electrode materials,porous carbon materials meet most of the requirements of supercapacitors due to their outstanding advantages such as excellent cycling performance,safety and stability,high specific capacitance,good electrical conductivity,and low price,and become the preferred electrode material for commercial supercapacitors.Therefore,it is quite important to design and synthesize porous carbon materials with high specific capacitance and high energy density.In this paper,versatile template method is utilized to design and synthesize mesoporous carbon spheres and nitrogen-doped three-dimensional porous hollow carbon nanospheres with controllable porous hollow structure and ultrahigh energy density.The morphologies of the carbon nanospheres were observed and properties are characterized.Finally,the electrochemical performances of the carbon electrode material in three different electrolyte systems were tested when assembled into supercapacitor.The main research contents and results of this paper are as follows:（1）M-phenylenediamine or m-aminophenol as raw materials.The amino groups as electron donor groups could increase the reaction activity to form resin,and succeed in introducing abundant in-situ nitrogen-doping.Colloidal silica as hard template and F127 as soft template can finely control the pore size distribution.After the etching of template and activation process,mesoporous carbon spheres and porous carbon nanospheres with interconnected porous hollow structure were finally fabricated.（2）The microstructure and chemical structure of the obtained porous carbon materials were characterized by SEM,TEM,BET,XRD,XPS and Raman spectroscopy.The porous structures of mesoporous carbon spheres and porous hollow carbon nanospheres were observed by SEM and TEM,and in-situ nitrogen atom doping was observed from the element distribution.The BET test confirmed that the specific surface area of the material is as high as 2044 m² g^-1 and rich micro-mesoporous structure were fabricated.Also,the obtained pore size（>0.7 nm）is larger than that of most electrolyte ions（～0.7 nm）,which means that electrolyte ions can enter these micro-mesoporous structures and participate in the electrochemical energy storage process efficiently.（3）The material was prepared as an electrode sheet and the electrochemical performance in supercapacitors were tested.In supercapacitors with different electrolytes（6M KOH,TEABF₄/AN,EMIBF₄）,the porous carbon nanospheres electrode material can show excellent electrochemical performance.（4）The material exhibits high specific capacitance(up to 233.9 Fg^-1 at a current density of 0.5 Ag^-1)in the ionic liquid electrolyte（EMIBF₄）due to the in-situ nitrogen doping,rich microporous structure and hollow structure inside the carbon nanospheres.Under high operating voltage（3.8V）,the material is very stable and achieved good cycling stability（91%retained after 20,000 cycles）,ultrahigh energy density(114.8 Wh kg^-1)and power density(15.35 kW kg^-1).