Journal
ELECTROCHIMICA ACTA
Volume 55, Issue 3, Pages 927-934Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2009.09.077
Keywords
Li-ion cells; Storage; Safety; Microstructure; Impedance
Categories
Funding
- National Natural Science Foundation of China [20773157]
- Project of Excellent Academic Pacemaker of Shanghai [07XD14035]
Ask authors/readers for more resources
A series of Li-ion cells with a LiCoO(2) cathode, artificial graphite anode and a LiPF(6)-based nonaqueous electrolyte were stored at 55 degrees C in a series of state of charge (SoC) from 0 to 100%. After storage, all the cells except the one stored in 0% SoC exhibited capacity fade and cycling performance decline which, were aggravated by increasing storage SoC. Furthermore, storage at higher SoC increased the safety risk of the cells. The cells stored at SoC higher than 50% could not pass the 3 C/5 V overcharge test, while such a test was easy to pass for the fresh cells and those stored at 0% SoC. The above results show that the fully discharged state is a favorable storage condition to maintain good storage performance of Li-ion cells. In addition, to clarify the aging mechanisms of the cells, XRD (X-ray diffraction), SEM (scanning electron microscopy) and EIS (electrochemical impedance spectra) measurements were carried out. The results indicate that the performance fading of the stored cells is not due to the bulk structure change of the electrode materials, but instead due to the microstructure variation of the cathode including the, decrease in the crystallite dimension, the change of the micro-stress, and the precipitation of the surface films over the electrodes. According to EIS analysis, the increase of the cathode impedance may be the main contributor to the overall degradation of the Li-ion cells after storage. (C) 2009 Elsevier Ltd. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available