天然石墨球-热解炭核壳结构的制备及电化学性能研究

通过化学气相沉积的方法,以乙炔为碳源,天然石墨球为原料,采用不同流化床CVD工艺和不同的反应时间,制备出具有光滑表面或颗粒状热解炭包覆层的核-壳构型改性天然石墨球.改性天然石墨球的核体是具有高度有序石墨结构的天然石墨,而壳体是无序结构的热解炭.与天然石墨球相比,具有核-壳结构的改性天然石墨球的首次库仑效率和循环性能都得到显著改善.尤其是具有颗粒状热解炭包覆层的改性石墨具有优异的循环性能,在41次循环后其放电容量仍为首次容量的84%,这一改善归因于表面沉积的颗粒状热解炭有效地降低了改性天然石墨颗粒之间的接触电阻和增加了接触面积.

Improving the electrochemical properties of natural graphite spheres by coating with a pyrolytic carbon shell

Two kinds of modified natural graphite (MNG) spheres with a pyrolytic carbon shell on smooth or granular surface were obtained using fluidized bed chemical vapor deposition of acetylene by adjusting the reaction parameters. The core of the MNG has a highly ordered graphite structure and the shell has a disordered structure. Compared with na￣tural graphite (NG) spheres, MNG with a core-shell structure shows improved first cycling efficiency and cyclability. Especially, the MNG spheres with a granular surface possess 84% retention of the first discharge capacity after 41cycles, owing to effective decrease of the contact resistance and increase of contact area between the MNG spheres.