Evolution of lithiation thermodynamics with the graphitization of carbons |
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Authors: | Y Reynier R Yazami B Fultz I Barsukov |
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Affiliation: | 1. Caltech CNRS International Laboratory on Materials for Electrochemical Energetics, Division of Engineering and Applied Science, California Institute of Technology, MC 138-78, Pasadena, CA 91125, USA;2. Superior Graphite Co., 10 S. Riverside Plaza, Chicago, IL 60606, USA |
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Abstract: | Instrumentation was developed to study the thermodynamics of lithium intercalation in cokes that were heat-treated at different temperatures. The method measures the open circuit voltages of electrochemical cells as a function of temperature, and obtains the entropy and enthalpy of the lithiation reaction. X-ray diffractometry and Raman spectroscopy were used to determine the structure of the carbon materials after heat treatment. The effect of the degree of graphitization on the entropy and enthalpy of lithium intercalation was thereby determined. A model is proposed to correlate the degree of graphitization to entropy profiles. It is shown that graphs of entropy versus open circuit voltage for different states of charge give quantitative information on graphitization, making them useful for the structural characterization of partially-graphitized carbons. |
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Keywords: | Carbon Graphite Lithium Thermodynamics Entropy |
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