The transformation of graphite electrode materials in lithium-ion batteries after cycling

The transformation of graphite electrode materials in lithium-ion batteries after cycling

TitleThe transformation of graphite electrode materials in lithium-ion batteries after cycling
Publication TypeJournal Article
Year of Publication2015
AuthorsKehua Dai, Zhihui Wang, Guo Ai, Hui Zhao, Wen Yuan, Xiangyun Song, Vincent S Battaglia, Chengdong Sun, Kai Wu, Gao Liu
JournalJournal of Power Sources
Volume298
Pagination349 - 354
Date Published01/2015
ISSN03787753
Abstract

To reveal how graphite electrodes change with cycling in lithium-ion batteries, electrochemical experiments involving charge-discharge cycling at different current density conditions are performed on commercial pouch cells and the graphite electrodes after cycling. This research shows that the polyvinylidene fluoride (PVDF) binder does not degrade, confirmed by the stable molecular weight after different cycling conditions. Particle size analysis results indicate that the diameter of graphite particles after cycling is ∼10% larger than that of the graphite before cycling, which results in a ∼30% volume expansion after cycling. For the cells cycled at the same current density, the graphite particle size increases with cycle time. For the cells with the same cycle numbers, the graphite particle size is larger in the cells cycled at lower current density. X-ray diffraction characterization shows that the d-spacings of the graphite particles in all the cells at different cycling conditions are identical. These results suggest that the graphite particle size increase associated with cycling may arise specifically when primary particles inflate the secondary particle size, leading to dramatic volume expansion of graphite secondary particles.

DOI10.1016/j.jpowsour.2015.08.055
Short TitleJournal of Power Sources
Refereed DesignationRefereed