Preparation And Capacitance Properties Of Graphene-Based Composites

Graphene exhibits excellent electrochemical performance due to its large specific surface areas,superior electronic conductivity and powerful mechanical properties.Thus graphene-based materials were regared as research subjects to improve the specific capacitance,cycle stability and rate performance of supercapacitors.Two electrode materials were investigated in this work;include polyaniline/vertical graphene/Ti electrode and boron-doped graphene/TiO₂ nanotube/Ti electrode.The PANI/VG/Ti electrode was prepared by using DC arc plasma jet CVD to deposite VG layer onto the Ti substrate.And PANI nanowires were prepared the VG layer by electropolymerization.The PANI nanowire possessed good conductivity,because network structure reduced interface resistance and improved contact area between the electrode and the electrolysis.The intrisic tantalum capacitance greatly increased the specific capacitance of the electrode.The porous structure of VG nanosheets enhanced the electron mobility,increasing the rate and cycle stability of the electrode.The PANI/VG/Ti electrode exhibited high specific capacitance in a 0.5 M H₂SO₄ electrolyte.The specific capacitance was 535.7F·g^-1 at current density of 40 A·g^-11 and the specific capacitance is 461 F·g^-1 under scan rate of50 mV·s^-1.The symmetrical supercapacitor consisted by PANI/VG/Ti electrode has a high energy density of 26.1 Wh·kg^-1 at a power density of 383 W·kg^-1 and a high power of 4.2kW·kg^-1 at an energy density of 6.95 Wh·kg^-11 density.The specific capacitance retained 86%of the initial specific capacitance after 10,000 cycles,showing excellent cycling stability.Boron-doped graphene has high lithium ion adsorption capacity,big specific capacitance,good electrical conductivity and stable structure.One-dimensional TiO₂ nanotubes have large specific surface area,strong adsorption capacity of lithium ions and fast electron transfer rate.The introduction of boron-doped graphene can make up for the deficiencies of low conductivity and slow reaction rate of TiO₂ nanotubes,thus improving the performance of lithium ion energy storage devices.TiO₂ nanotube array was prepared by electrochemical anodization,and BG film was prepared by EA-CVD,then constructing a BG/TiO₂/Ti electrode.Symmetrical supercapacitor constructed with BG/TiO₂/Ti electrode can achieve a wide operating potential of 2.6 V in CMC/LiCl gel electrolyte.The supercapacitor can provide 221.8 Wh·kg^-1 at a power density of 5.98 kW·kg^-1;When the power density is 35.1kW?kg^-1,the energy density can maintain at 102.4 Wh?kg^-1;This supercapacitor exhibited a long electrochemical lifetime,and the specific capacitance maintained 91.3%of the initial specific capacitance after 10,000 cycles.