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 J. Electrochem. Sci. Technol > Volume 2(1); 2011 > Article
 Article Journal of Electrochemical Science and Technology 2011;2(1):45-50. DOI: https://doi.org/10.5229/JECST.2011.2.1.045
 Expanded Graphite Negative Electrode for Lithium-ion Batteries Hyun-D. Yoo, Ji-Heon Ryu, Seong-Ho Park, Yu-Won Park, Bok-H. Ka, Seung-M. Oh Department of Chemical and Biological Engineering and WCU program of C2E2 Seoul National University;Graduate School of Knowledge-based Technology and Energy, Korea Polytechnic University;Department of Chemical and Biological Engineering and WCU program of C2E2 Seoul National University;Department of Chemical and Biological Engineering and WCU program of C2E2 Seoul National University;Department of Chemical and Biological Engineering and WCU program of C2E2 Seoul National University;Department of Chemical and Biological Engineering and WCU program of C2E2 Seoul National University; Abstract A series of expanded graphites is prepared from graphite oxide by changing the heat-treatment temperature, and their lithiation/de-lithiation mechanism and rate performance are examined. A featureless sloping profile is observed in their charge-discharge voltage and dilatometry profiles, which is contrasted by the stepwise plateau-like profiles observed with the pristine graphite. With an increase in the heat-treatment temperature from $250^{circ}C$ to $850^{circ}C$, the interlayer distance becomes smaller whereas the electric conductivity becomes larger, both of which are resulted from a removal of foreign atoms (mainly oxygen) from the interlayer gaps. The expanded graphite that is prepared by a heat-treatment at $450^{circ}C$ delivers the best rate performance, which seems to be a trade-off between the $Li^+$ ion diffusivity that is affected by the interlayer distance and electrical conductivity. Key Words: Lithium-ion batteries, Expanded graphites, Electrochemical dilatometry, Interlayer distance, Electrical conductivity