TG-MS analysis of solid electrolyte interphase (SEI) on graphite negative-electrode in lithium-ion batteries

• Published in: Journal of power sources Vol. 161; no. 2; pp. 1275 - 1280
• Main Authors: Zhao, Liwei, Watanabe, Izumi, Doi, Takayuki, Okada, Shigeto, Yamaki, Jun-ichi
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.10.2006; Elsevier Sequoia
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Graphite negative-electrode; Lithium-ion battery; Solid electrolyte interphase; Thermal analysis; Graphite negative-electrode; Lithium-ion battery; Solid electrolyte interphase; Thermal analysis; Natural graphite; Anode; Chemical stability; Solid electrolyte; Chemical structure; Thermogravimetry; Secondary cell; Differential thermal analysis; Lithium carbonate; Thermal stability; Lithium battery; Intercalation compound; Photoelectron spectrometry; Current density; Mass spectrometry; Lithium ion
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2006.05.045

The thermal stability and chemical structure of solid electrolyte interphase (SEI) formed on a natural-graphite negative-electrode in ethylene carbonate (EC) and dimethyl carbonate (DMC)-based electrolyte was investigated by thermogravimetry-differential thermal analysis combined with mass spectrometry (TG-DTA/MS) and X-ray photoemission spectroscopy (XPS). Due to the decomposition of SEI, two CO 2 evolution peaks at around 330 and 430 °C were detected in TG-MS studies with continuous CO 2 background. The continuous CO 2 background was attributed to the gradual decomposition of oxygen-containing polymeric species of SEI. Another two dominant components of SEI, lithium alkyl carbonate and lithium oxalate, were found to contribute to the CO 2 peaks at 330 and 430 °C separately. The effects of charging-depth, current density and cycle number on the CO 2 distribution and XPS spectra were studied. It was found that lithium oxalate was reduction product of lithium alkyl carbonate during the intercalation of lithium ions. The reduction reaction could be accelerated by elevated temperature. The transformation of SEI chemical structure showed direct effect on the thermal stability of SEI. At the same time, lithium carbonate was also found in SEI on the graphite electrode after long cycles, while it was negligible in the electrode subjected to short cycles.