Synthesis of Nanomesh Graphene and Their Application as High Performance Electrodes in Supercapacitors

Author:Zuo Yan Fang

Supervisor:ning guo qing


Degree Year:2018





Supercapacitors have received much attention as an effeicent energy storage device.Graphene is used as electrode material for supercapacitors because of its large specific surface area,uniform pore size,good electrical conductivity and stable mechanical properties.Graphene stack between neighboring layers easily and the surface is hydrophobic.In this paper,the defects are improved by controlling structure,doping,high temperature stability and loading to improve electrochemical performance.(1)S,N dual-doped graphene whisker(SNGF)was successfully prepared by CVD method using magnesium sulfate whiskers as template and sulfur source,ethylene as carbon source and ammonia as nitrogen source.SNGF has a fibrous porous structure.S,N are successfully incorporated into the graphene lattice network;SNGF has a higher specific capacity(311 F/g at 0.25 A/g),a good rate performance,good cycle performance,high energy density and power density.(2)Nanomesh graphene(NMG)was synthesized by CVD method using porous magnesium oxide as template,methane as carbon source.Sulfur-decorated nanomesh graphene(S@G)was prepared by mechanically mixing and heating the NMG and sulfur.S@G has a porous multi-corrugations morphology,sulfur content is up to 2.37 atom%,better conductivity and more excellent hydrophilicity;S@G5 has a higher specific capacity(257 F/g at 0.25A/g),good rate performance,excellent cycle performance.(3)Nanomesh graphene synthesized by ethylene cracked was calcined at different temperatures without or with template,respectively.The experimental results show that the structure of graphene calcined without template was damaged and the electrode performance decreases.The structure of graphene calcined with template remains well,the specific surface area increases.In the electrochemical tests,the specific capacity of900NMG increases(specific capacity of 275 F/g at 0.25A/g),and has better rate performance,good cycle performance,the power density and energy density increase.(4)The unburned NMG and Ni(NO3)2 solution were impregnated and then calcined to obtain a NiO-loaded graphene(NiO@G-1,NiO@G-2,NiO@G-3).The experimental results show that NiO particles are successfully supported on the graphene sheets and fixed in the graphene pores.NiO@G-3 has a higher specific capacity(specific capacity of 138 F/g at 1A/g),Asymmetric capacitor builded up by NiO@G-3 and NMG has better rate performance,cycle performance,and high energy density and power density.