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J. Electrochem. Sci. Technol > Volume 2(1); 2011 > 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


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