Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6613642 | Electrochimica Acta | 2014 | 9 Pages |
Abstract
Graphene paper that exhibits an excellent stabilized capacity, as high as 1300 mAh gâ1 at a current rate of 60Â mAÂ gâ1, as a lithium ion battery anode is fabricated and evaluated. The few-layer graphene used to make the graphene paper is prepared via the thermal reduction of graphite oxide. The graphene is then modified by a novel method utilizing inherent defects, namely epoxy groups, on the graphene as active sites for a reaction with methanol, 1-butanol, 1-hexanol, and 1-octanol. The density values and X-ray diffraction patterns obtained for the graphene paper demonstrate that the alkyl brushes on the graphene sheets expand the d-spacing and hinder close restacking of the sheets, thereby inducing the formation of extra cavities within the paper. This loose packing due to the alkyl brushes increases sensitively as the alkyl chain length of the alcohol becomes longer. The lithium ion insertion capacity of a graphene paper electrode at the first cycle also increases with the alkyl chain length. However, fading of the capacity at early charge/discharge cycles is accelerated by the modification process because of electrolyte penetration into the gallery and the acceleration of protective solid electrolyte interface film formation due to looser packing. The paper composed of graphene modified with 1-butanol rather than shorter or longer alcohols exhibits the best reversible storage capacity, more than two-fold higher when compared to that of pristine graphene paper, due to a compromise between two conflicting effects on the reversible storage capacity by long alkyl brushes. The tensile properties and electrical conductivity of the graphene papers are also examined.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
Kyung Min Oh, Sung-Woo Cho, Gyeong-Ok Kim, Kwang-Sun Ryu, Han Mo Jeong,