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

JOURNAL OF POWER SOURCES

卷:298

Article

Dai, Kehua^1,2  Wang, Zhihui^1,3  Ai, Guo¹  Zhao, Hui¹  Yuan, Wen¹  Song, Xiangyun¹  Battaglia, Vincent¹  Sun, Chengdong⁴  Wu, Kai⁴  Liu, Gao¹ 

[1] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Energy Technol Area, Berkeley, CA 94720 USA

[2] Northeastern Univ, Sch Met & Mat, Shenyang 110004, Peoples R China

[3] Zeptor Corp, Menlo Pk, CA 94025 USA

[4] Ningde Amperex Technol Co Ltd, Res Inst, Ningde, Fujian, Peoples R China

关键词: Lithium-ion battery;    Anode;    Graphite;    Poly(vinylidene fluoride);    Stability;    Volume expansion;   

DOI  :  10.1016/j.jpowsour.2015.08.055

来源: Elsevier

【 摘 要 】

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 similar to 10% larger than that of the graphite before cycling, which results in a similar to 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. Published by Elsevier B.V.

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