Preparation And Energy Storage Properties Research Of Graphitized Mesophase Carbon Microbeads@Carbide Derived Carbon

Mesophase carbon microbeads as a kind of graphite materials were widely used as anode materials of lithium ion battery due to their high conductivity,high diffusion coefficient of lithium ion,high capacity of lithium intercalation and low potential of lithium ion intercalation.This paper focused on designing graphitized mesophase carbon microbeads?GMCMB?@carbide derived carbon composites?GMCMB@MC-CDCs?with core@shell structure,The composites were used as the anode materials of lithium ion battery to improve the capacity,rate and cycling performances.Graphitized mesophase carbon microbeads@carbide?GMCMB@MC,M is on behalf of metal?precursors were prepared by solid reaction of GMCMB as carbon source and different transition metals with different molar ratios of GMCMB/M at 1200? for 2h.Graphitized mesophase carbon microbeads@carbide derived carbon?GMCMB@MC-CDCs?composites with core-shell structure were obtained by etching GMCMB@MC precursors under Cl₂ at different etching temperatures for 1h.The composition,morphology and structure of composites were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,Raman spectroscopy,transmission electron microscopy?TEM?and N₂ adsorption/desorption analysis.The electrochemical properties of GMCMB@MC-CDCs for anode materials of lithium ion battery were evaluated using galvanostatic charging-discharging measurement,rate performance,cyclic voltammetry and electrochemical impedance spectroscopy?EIS?measurement.The main results are as follows:?1?GMCMB@NbC precursors were successfully prepared by solid phase method and a series of GMCMB@NbC-CDCs composites were synthesized by etching GMCMB@NbC precursors under Cl₂ for 1h.GMCMB@MC-CDCs demonstrated a core-shell structure with GMCMB as core and MC-CDCs as shell with pore size lower than 2nm.?2?The micropore structure and ordering degree of CDC can be tuned by controlling the etching temperature,consequently adjusting the specific surface area and pore volume to improve the specific capacity,rate performance and cycling performance of lithium ion battery.The results indicated that the specific surface area of GMCMB@NbC-CDCs chlorinated at 800 ? is relatively higher,reaching to 347.1m²×g^-1,and 0.20 cm³×g^-1 of pore volume.And the initial charge capacity and discharge capacity are 726.9 mAh×g^-1 and 458.9 mAh×g^-1,respectively.?3?The thickness of CDC shell and size of GMCMB core can be effectively tuned by selecting appropriate molar ratio of GMCMB/Nb,thus tuning the specific surface area and pore volume.The initial discharge capacity of GMCMB@NbC-CDCs prepared with molar ratio 2/1 of GMCMB/Nb used as lithium ion battery anode material-can achieve to 458.9 mAh×g^-1,and can remain 399.5 mAh×g^-1 after 50 cycles,with 87.1%capacity retention and better cycling performance.However,GMCMB@NbC-CDCs prepared with malor ratio 3/1 of GMCMB/Nb has a better rate performance.?4?GMCMB@NbC,GMCMB@TiC,GMMCB@TaC and GMCMB@VC precursors were successfully prepared by solid phase method at 1200oC.A series of GMCMB@MC-CDCs composites were obtained by etching the corresponding precursors.The specific capacity of GMCMB@NbC-CDCs for lithium ion battery can be effectively improved by choosing appropriate carbide precursor.The specific surface area and pore volume of the composites reached the maximum when GMCMB@NbC was used as the precursor.And it manifested highest specific capacity when used as anode materials of lithium ion battery.