Functionalization of Carbon Materials as Energy Conversion Materials by Surface Modification

1.石油焦的表面氟化、氟化过程及电化学行为石油焦(原焦经1860℃、2300℃和2800℃热处理)分别在150℃、200℃和300℃下用0.3bar F_2氟化2分钟。原始石油焦有一定程度的氟化，而其他热处理焦炭的氟化程度较低。1860℃和2300℃热处理的石油焦经氟化处理后BET比表面积略有减小，而2800℃热处理的石油焦的BET比表面积增加。所有焦炭都同时增加了直径为5-15 nm的中孔。用X射线衍射仪和拉曼光谱研究了室温、380℃和515℃氟化条件下石墨的氟化过程。首先形成具有sp2平面石墨烯的氟插层相，然后转化为具有褶皱石墨烯层的氟化石墨。表面氟化石油焦的容量和一次库仑效率分别提高了10%和5-10%。以丙烷和氢气为原料，采用化学气相渗透(CVI)法在95 0℃下将热解碳渗透到碳化滤纸中。与碳化滤纸相比，渗透热解碳具有更高的结晶度和更小的表面积。热解碳的库仑效率提高了10-15%，这可能是由于溶剂分解减少所致。氟化物添加剂对石墨电极性能的改善在1M LiClO_4-碳酸乙二酯/碳酸二乙酯溶液中考察了含氟酯和醚的性能。少量氟化合物的加入改善了石墨电极在0℃~-10℃的充放电性能。这可能是因为石墨表面膜中的氟基团促进了Li^+离子的扩散。

1. Surface fluorination, fluorination process and electrochemical behavior of petroleum cokesPetroleum cokes (original, heat-treated at 1860℃, 2300℃ and 2800℃) were fluorinated at 150℃, 200℃ and 300℃ by 0.3 bar F_2 for 2 min. Original petroleum coke was somewhat fluorinated, however, the fluorination of other heat-treated cokes were less. BET surface areas of petroleum cokes heat-treated at 1860℃ and 2300℃ were slightly decreased by fluorination while that heat-treated at 2800℃ was increased. Meso-pores with diameters of 5-15 nm were simultaneously increased for all the cokes. Fluorination process of graphite was monitored by X-ray diffraction and Raman spectroscopy for samples fluorinated at room temperature, 380℃ and 515℃. Fluorine-intercalated phase with sp^2 planar graphene layers is formed at first, and then converted to graphite fluoride with puckered graphene layers. The capacities of surface-fluorinated petroleum cokes and first coulombic efficiencies were increased by 10% and 5-10%, respectively.2. Functionalization of carbon materials by chemical vapor infiltration (CVI)Pyrocarbon was infiltrated into carbonized filter paper at 950℃ by CVI method using propane and hydrogen. Infiltrated pyrocarbon has higher crystallinity and smaller surface area than carbonized filter paper. Coulombic efficiency of the pyrocarbon was increased by 10-15% probably due to decrease in the solvent decomposition.3. Improvement of characteristics of graphite electrode by fluoride additivesFluorine-containing esters and ethers were examined in 1M LiClO_4-ethylene carbonate/diethyl carbonate solution. Addition of a small amount of fluorine compound improved the charge/discharge characteristics of graphite electrode at 0℃〜-10℃. This may be because fluorine groups incorporated in the surface film on graphite facilitates the diffusion of Li^+ ion.