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Intercalation of Lithium in Pitch-Based Graphitized Carbon Fibers Chemically Modified by Fluorine: Soft Carbon With or Without an Oxide SurfaceThe effects of carbon structure and surface oxygen on the carbon's performance as the anode in lithium-ion battery were studied. Two carbon materials were used for the electrochemical tests: soft carbon made from defluorination of graphite fluoride, and the carbon precursor from which the graphite fluoride was made. In this research the precursor was graphitized carbon fiber P-100. It was first fluorinated to form CF(0.68), then defluorinated slowly at 350 to 450 C in bromoform, and finally heated in 1000 C nitrogen before exposed to room temperature air, producing disordered soft carbon having basic surface oxides. This process caused very little carbon loss. The electrochemical test involved cycles of lithium intercalation and deintercalation using C/saturated LiI-50/50 (vol %) EC and DMC/Li half cell. The cycling test had four major results. (1) The presence of a basic oxide surface may prevent solvent from entering the carbon structure and therefore prolong the carbon's cycle life for lithium intercalation-deintercalation. (2) The disordered soft carbon can store lithium through two different mechanisms. One of them is lithium intercalation. which gives the disordered carbon an electrochemical behavior similar to its more ordered graphitic precursor. The other is unknown in its chemistry, but is responsible for the high-N,oltage portion (less than 0.3V) of the charge-discharge curve. (3) Under certain conditions, the disordered carbon can store more lithium than its precursor. (4) These sample and its precursor can intercalate at 200 mA/g. and deintercalate at a rate of 2000 mA/g without significant capacity loss.
Document ID
20000018015
Document Type
Conference Paper
Authors
Hung, Ching-Chen
(NASA Glenn Research Center Cleveland, OH United States)
Prisko, Aniko
(Cleveland State Univ. Cleveland, OH United States)
Date Acquired
September 7, 2013
Publication Date
December 1, 1999
Subject Category
Chemistry And Materials (General)
Report/Patent Number
E-11914
NASA/TM-1999-209437
NAS 1.15:209437
Meeting Information
Carbon(Charleston, SC)
Funding Number(s)
PROJECT: RTOP 632-1A-1E
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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