Preparation And Eectrochemical Performance Of Carbon Pillared Graphene Composite

The development of new energy vehicles and the popularization of electronic equipment has made higher demands on the energy density,rate performance and lifespan of lithium ion batteries(LIBs).Therefore,it is is extremely important to design and prepare the high performance electrode materials for LIBs.Graphene has been considered to be a promising candidate as energy material for LIBs and supercapacitors because of its huge specific surface area,excellent electronic conductivity and fast electron migration rate.However,graphene is used as anode material directly with large irreversible capacity,low initial columbic efficiency,poor rate and cycle performance.Herein,carbon pillared graphene composites are fabricated by inducing self-assemble and subsequent pyrolysis reduction treatment,which is to use kinds of polymer and graphene oxide(GO)as raw material,taking advantage of rich chemical modification and easily induce self-assembled properties of graphene oxide prepared by chemical oxidation.The effects of surfactant modification,carbon precursor kinds,the mass ratio of carbon precursor and GO on the structure and electrochemical properties of carbon pillared graphene composites were studied.The research contents and results are as follows:(1)Polyacrylic acid-carbon pillared graphene composites(PAGR)and CTAB modified PAGR(CT-PAGR)are prepared by solution evaporation induced self-assemble and subsequent pyrolysis reduction treatment.The structure and electrochemical properties of pure graphene(GR),PAGR and CT-PAGR were compared.The effects of CTAB on the structure and electrochemical properties of PAGR were investigated.The results showed that polyacrylic acid-carbon pillars actually improve the structure and electrochemical stability of the graphene.PAGR sample exhibits a reversible high capacity of 411 mAh/g and high first coulomb efficiency of 52.6% at a current density of 100 mA/g,superior to the pristine graphene(340 mAh/g and 48.6%).The CT-PAGR composite shows poor electrochemical performance with a reversible low capacity of 302 mAh/g and low first coulomb efficiency of 31.5% at a current density of 100 mA/g,which is far lower than GR and PAGR.CTAB reduced the hydrophilicity of GO and reduced the electrochemical performance of PAGR.(2)The high nitrogen content carbon precursor of melamine(Mel)monomers is easily absorbed on the GO surface by π-π conjugation.Melamine-carbon pillaredgraphene composite(MGR)is prepared with ultrasonic-assisted dispersion,solution evaporation induced self-assemble and subsequent pyrolysis reduction treatment.MGR includes N elements with content of ca.8.43 atom% and pyridinic nitrogen content closed to 50%,which superior to most N-doped graphene.When employed as an anode material for LIBs,MGR sample exhibits a high reversible capacity of512 mAh/g and high first coulomb efficiency of 57.2% at a current density of 100mA/g,and an excellent rate capability of 272 mAh/g at a current density of 1 A/g.However,melamine-carbon is not enough stable because of small molecule organic,resulted in poor cycle stability.(3)Polyaniline-carbon pillared graphene composites(PGR)are prepared by vacuum extraction induced self-assemble and subsequent pyrolysis reduction treatment.The effects of the mass ratio of aniline monomer(AN)and graphene oxide(GO)on the structure and electrochemical properties of PGR were investigated.The results showed that polyaniline-carbon pillars effectively improve the structure and electrochemical stability of the graphene.PGR1 sample prepared by the mass ratio of 1:1 of AN and GO exhibits a high reversible capacity of 653 mAh/g at a current density of 100 mA/g and an excellent rate capability of 343 mAh/g at a current density of 1 A/g,more than three times as much as the pure graphene sample(101mAh/g).