报告题目：Template-directed oxide growth on aligned CNTs and its application in lithium ion batteries

　　报 告 人：吴扬 博士

　　单　  位：清华大学

　　报告时间：2014年4月25日 (星期五)上午09:00

　　报告地点：中国科学院长春应用化学研究所无机分析楼1号会议室

　　附：报告人简介及报告内容摘要

　　Mr. Yang Wu received his M.S. in physics with Prof. Shoushan Fan from Tsinghua University in 2005. After he graduated from Tsinghua, he was admitted by Arizona State University in U.S. to start his Ph.D study with Prof. Ulrich Haussermann. Currently, he is a postdoctoral associate with Prof. Shoushan Fan at Tsinghua-Foxconn Nanotechnology Research Center. His current research interest is the electrochemical energy storage materials. Mr. Yang Wu has published more than 20 papers in high impact scientific journals. He has also filed more than 20 patents from 2005 and 9 was issued. His effort in exploring novel thermoelectric materials in the Zn-Sb-In ternary system has been selected as one of the recipients of Ludo-Frevel Scholarship by ICDD in 2010.

　　Transition metal oxides have recently been identified as a promising candidate for the anode material of lithium ion batteries (LIBs). The reversible lithium storage in transition metal oxides takes place via a conversion mechanism. In contrast to prevalent synthesis that requires delicate wet chemistry methods, we employed ordered carbon nanotube (CNT) films to template the growth of nano-sized oxides, e.g. Fe3O4, via a sputtering approach. Such CNT films were directly drawn from super-aligned CNT arrays grown on 8-inch silicon wafers. The Fe deposition was spontaneous converted to a Fe3O4 sheath presumably by the O2 in the ambient. The complete oxidation was confirmed with XRD and XPS. The electrochemical characterization suggested that the specific capacity of CNT-Fe3O4 composite anodes was dependent on the size of the Fe3O4 coating. As the average size of Fe3O4 was regulated to ca. 7 nm (correspondingto 60 wt% of Fe3O4), the optimal capacity of CNT-Fe3O4 anodes was achieved (1200mAh g-1with a 90% capacity retention after 100 cycles, or 800 mAh g-1based on the total mass). The specific capacity of over 1100 mAhg-1 at 1C rate was also remarkable.The excellent electrochemical performance could be attributed to CNTs that served as both scaffolds and conductors. Finally, the contribution of CNT in the same voltage window (0.1-3V) and plausible originations to the extra specific capacity will be discussed.