球形天然石墨酚醛树脂二次包覆工艺及其对性能的影响

Effect of double phenol-formaldehyde resin carbon-coating process on performances for spherical graphite

以酚醛树脂为碳源,前驱体液相浸渍包覆球形天然石墨在1 000℃碳化,利用XRD,Raman,SEM,TEM和BET等分析方法,研究一次包覆、二次包覆及环己醇改善固液界面等不同包覆工艺对材料表面结构、形貌和电化学性能的影响。研究结果表明:包覆后样品表面变得光滑,石墨化度降低,表面各向同性程度增加,比表面积由6.934 m2/g增加至10.877 m2/g;添加环己醇并二次包覆改性的样品效果最好,首次不可逆容量降低,由98.0mA·h/g减小至37.3 mA·h/g,首次库伦效率由73.2%提高到90.2%,0.2C循环50次后容量保持率为98.7%。

The surface of graphite was coated with amorphous carbon in phenol-formaldehyde resin mixing in a liquid phase. Then the graphite samples were carbonizated at 1 000 ~C. The carbon-coating samples were prepared by three different process including one time coating, double coating and the improvement of interface properties by adding cyclohexanol. The surface structure and morphology of samples were investigated by XRD, Raman, SEM, TEM and BET. Electrochemical behaviors of samples were studied by galvanostatic charge/discharge test. The results show that the flake particles of the spherical graphite exhibits smooth surface with the decrease of graphitization and a enhancement of isotropic. Specific surface area increases from 6.934 m2/g to 10.877 m2/g. The sample by adding cyclohexanol shows the best electrochemical property with lower irreversible capacity from 98.0 mA.h/g to 37.3 mA.h/g, higher coulomb efficiency from 73.2% to 90.2%, and the specific capacity keeping at 98.7% after 50 cycles with charging and discharging in 0.2C.