Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
Langmuir. 2010 Sep 21;26(18):14990-4. doi: 10.1021/la1019857.
A relation between the amount of edge orientations and the kinetics of lithium-ion intercalation at the basal plane of highly oriented pyrolytic graphite (HOPG) was studied. The fraction of edge orientations (f(edge)) exposed on the basal plane of HOPG was evaluated from the kinetics of heterogeneous electron transfer of Ru(NH(3))(6)(2+/3+). Obtained f(edge) values ranged from 0.025 to 0.067, which were in good agreement with those previously reported. The charge-transfer resistance (R(ct)) for lithium-ion intercalation at the same HOPG samples was evaluated by ac impedance spectroscopy in an electrolyte consisting of 1 mol dm(-3) LiClO(4) dissolved in a mixture of ethylene carbonate/dimethyl carbonate (1:1 by vol). A clear correlation was observed between the f(edge) and R(ct) values at the basal plane of 15 HOPG samples, and the edge-area specific resistance was evaluated to be ca. 200 Ω cm(2) at the electrode potential of 0.2 V versus Li/Li(+). These results indicate that the amount of edge orientations is one of the determining factors in the kinetics of lithium-ion intercalation at graphite.
研究了高度取向石墨（HOPG）基面中边缘取向的数量与锂离子嵌入动力学之间的关系。通过 Ru(NH(3))(6)(2+/3+)的异质电子转移动力学，评估了 HOPG 基面中暴露的边缘取向分数（f(edge)）。得到的 f(edge)值范围为 0.025 至 0.067，与之前报道的值吻合较好。在由碳酸乙烯酯/碳酸二甲酯（1:1 体积比）混合溶液中溶解 1 mol dm(-3) LiClO(4)的电解质中，通过交流阻抗谱评估了相同 HOPG 样品中锂离子在基面中的嵌入的电荷转移电阻（R(ct)）。在 15 个 HOPG 样品的基面中，f(edge)和 R(ct)值之间观察到明显的相关性，在电极电势为 0.2 V 相对于 Li/Li(+)时，边缘面积比电阻被评估为约 200 Ω cm(2)。这些结果表明，边缘取向的数量是石墨中锂离子嵌入动力学的决定因素之一。
