Abstract The behavior of the electrolyte anion, tetrafluoroborate ( BF 4 - ), in an electric double-layer capacitor was studied by solid state 11 B NMR using two activated carbons of medium (M500) and large (M3000) surface area, which show capacitance of 35 F/ml and 20 F/ml by charging at 2.7 V, respectively. Magic angle spinning (MAS) 11 B NMR distinguishes two species (A and B) on the carbons at the impregnated, charged, and discharged stages. The A species corresponds to ions on the outer surface, showing free motion regardless of the activated carbon. The B species is located in the pores of the activated carbon, showing a downfield shift and line broadening. The B species in M500 was further separated into C and D species according to their chemical shifts in multiple quantum (MQ)MAS NMR. The very short relaxation time and large chemical shift of the C species suggest a very strong adsorption over the positive electrode of M500, whereas its spherical symmetry is maintained, as indicated by its small quadrupole constant. The amount of this species increases on the positive electrode of M500 by charging at 2.7 V, contributing to the larger capacitance (35 mF/ml) of this particular carbon at this voltage. By contrast, the B species was more moderately immobilized on the positive electrode of M3000, although the ion appeared to be deformed into a flattened shape on the carbon surface of large pores as indicated by its larger quadrupole constant. A rapid exchange between adsorbed and free B species within the same pores of larger size in M3000 may reduce the capacitance in spite of the more adsorption on this large surface area activated carbon.

中文翻译：

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11B 核磁共振研究 高炉4—— 有机电解质中 EDLCs 在不同充电阶段的活性炭中的阴离子

摘要 电解质阴离子四氟硼酸盐 (BF 4 - ) 在双电层电容器中的行为通过固态 11 B NMR 使用两种中等 (M500) 和大 (M3000) 表面积的活性炭进行研究，显示出电容通过以 2.7 V 充电，分别为 35 F/ml 和 20 F/ml。魔角纺丝 (MAS) 11 B NMR 在浸渍、充电和放电阶段区分碳上的两种物质（A 和 B）。A 物种对应于外表面的离子，无论活性炭如何都表现出自由运动。B 物质位于活性炭的孔隙中，表现出低场位移和谱线加宽。M500 中的 B 物种根据它们在多量子 (MQ) MAS NMR 中的化学位移进一步分离为 C 和 D 物种。C 物质的非常短的弛豫时间和大的化学位移表明在 M500 的正极上有很强的吸附，而它的球对称性保持不变，如其小的四极常数所示。通过以 2.7 V 充电，该物质在 M500 正极上的数量增加，从而导致该特定碳在此电压下具有更大的电容 (35 mF/ml)。相比之下，B 物质更适度地固定在 M3000 的正极上，尽管离子似乎在大孔的碳表面变形为扁平形状，如其较大的四极常数所示。