S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Chemical and Biological Engineering (화학생물공학부) Journal Papers (저널논문_화학생물공학부)
Preparation of Kevlar-derived carbon fibers and their anodic performances in Li secondary batteries
- Ko, Ki Seok; Park, Chul Wan; Yoon, Seong-Ho; Oh, Seung M.
- Issue Date
- Carbon 2001;39:1619–25.
- Carbon fibers; Heat treatment; Electrochemical analysis; Carbon yield; Electrochemical properties
- We report here the preparation of Kevlar-derived carbon fibers and the preliminary results on their anodic performances in Li secondary batteries. The single- or two-step carbonization process is employed for the preparation. In the single-step process, the Kevlar flocks are heat-treated under Ar atmosphere from 25 to 800°C with a heating rate of 5°C min−1, but an additional intermediate heating at a fixed temperature between 330 and 510°C for 2 h is applied in the two-step preparation. The two-step carbonization allows a higher carbon yield than that achieved in the single-step one (ca. 36%). In particular, a maximum yield (ca. 50%) is observed with an intermediate heating at 400–410°C. The infrared study indicates that the higher carbon yield achieved in the two-step process is indebted to the formation of condensed/cross-linked polyaromatic molecules during the intermediate heating period, which seemingly alleviates the volatile loss in the subsequent higher temperature heating. The Kevlar-derived carbon fibers exhibit the charge–discharge behaviors that are commonly observed in non-graphitizable carbons. Here, the carbon made by the two-step process (intermediate heating at 410°C) delivers a higher discharge capacity than the single-step ones. In particular, a notably high capacity near zero volts is observed in the two-step carbon that is associated with the Li+ removal from the micropores. The higher population of micropores in the two-step carbons may be explained by the enriched formation of cross-linked polyaromatics during the intermediate heating.
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