微晶碳电活化过程中离子尺寸效应研究

Influence of Ions Dimension on the Electric Field Activation of Micro-Crystallite Carbon

以石油焦基微晶碳作为电极材料,并由N2吸附,X射线衍射(XRD)表征其孔结构和微晶结构.研究了4种电解液Et4NBF4/PC(四乙基铵四氟硼酸盐/碳酸丙烯酯)、Et4NBF4/AN(四乙基铵四氟硼酸盐/乙腈)、Bu4NBF4/PC(四丁基铵四氟硼酸盐/碳酸丙烯酯)和Bu4NBF4/AN(四丁基铵四氟硼酸盐/乙腈)的微晶碳电容器特性.结果表明:电解质离子与溶剂AN的溶剂化半径较小,容易嵌入类石墨微晶碳层,其于AN的电活化电位比在PC中的低,致使电活化程度更深,材料的表面利用率更高,电容量较大.电解质阳离子(Et4N+,Bu4N+)大小对电活化影响不大.电活化使材料类石墨微晶层间距(d002)变大,离子尺寸越大,层间距增加越明显.

Micro-crystallite carbon （ CC） was synthesized by KOH activation of carbonized petroleum coke precursors. The porous properties structure and crystallite structure were characterized by N2 adsorption-desorption, X-ray diffraction （ XRD） measurements. The capacitive behavior of CC was investigated in the electrolyte of Et4NBF4 /PC,Et4NBF4 /AN,Bu4NBF4 /PC and Bu4NBF4 /AN,respectively. Results showed that the lower potential of electric field activation （ EFA） was obtained in the solvent of AN than in PC,which was ascribed to the fact that smaller solvated ions dimension in AN facilitating the intercalation of the solvated ions into micro-crystallite interlayer. The extent of EFA was more remarkable in AN under the same operating voltage due to its lower EFA potential; and consequently,produced the higher specific capacitance. With regarding to the Bu4NBF4 and Et4NBF4,little effect of cations size on the EFA process was observed,compared with that of solvent. After charge-discharged,micro-crystallite interlayer of CC swelled,indicating that the ion intercalation occurred during the EFA. And the interlayer expansion increased to a greater extent when the dimension of intercalated-ion was larger.