Preparation And Electrochemical Property Of Sphere-like Graphite@Silicon Carbide Derived Cabon

To meet the requirements of the energy storage materials for high energy densityand high power density, bifunctional carbon composites with core-shell structurewere prepared in this paper, which were composed of tailored porous carbide-derivedcarbon as the shell and graphitized carbon with excellent conductivity and a highenergy storage capacity as the core. Two types of sphere-like graphite carbonincluding graphitized mesophase carbon microbeads (GMCMB) and spherical naturalgraphite (NG) were used as carbon sources. GMCMB@SiC and NG@SiC werefirstly prepared by high temperature solid reaction of carbon and silicon. Thengraphitized mesophase carbon microbeads@silicon carbide-derived carbon(GMCMB@SiC-CDCs) and spherical natural graphite@silicon carbide-derivedcarbon (NG@SiC-CDCs) composites were obtained by chlorination. Thecomposition, structure, morphology, pore structure, specific surface area andelectrochemical properties of the composites were characterized and the energestorage mechanism was preliminarily discussed. The main conclusions are as follows:1. GMCMB@SiC-CDCs and NG@SiC-CDCs composites can be preparedsuccessfully by high temperature solid reaction and chlorination. The compositeshave typical core@shell structure, namely GMCMB and NG as the core respectively,and SiC-CDCs with micropore size less than1nm as the shell.2. Varying the molar ratio of C and Si, the thickness of the SiC-CDCs shell andthe size of the GMCMB/NG core can be rationally regulated. The specific surfacearea and pore volume can also be widely adjusted. Decreasing the molar ratio of Cand Si, the content of SiC-CDCs in the composites increases and the correspondingspecific surface area and pore volume also increase.3. The reversible capacity of negative electrode of Li-ion battery can beeffectively improved by choosing proper molar ratio of C and Si, which means theproper proportion of carbide derived carbon and sphere-like graphite. In addition, thecomposites showed better charge-discharge rates and higher capacity retention than GMCMB and NG.4. GMCMB@SiC-CDCs and NG@SiC-CDCs also exhibits excellentcapacitance performance when used as the electrode materials for supercapacitors,.With the decreasing of molar ratio of C and Si, the content of CDCs increases,leading to the increase of the specific capacitance and energy density. The compositesshow an excellent large current charge-discharge property.