Authors: H J Santner C Korepp M Winter J O Besenhard KC Möller
Publish Date: 2004/02/17
Volume: 379, Issue: 2, Pages: 266-271
Abstract
Lithiumion batteries operate beyond the thermodynamic stability of the aprotic organic electrolyte used and electrolyte decomposition occurs at both electrodes The electrolyte must therefore be composed in a way that its decomposition products form a film on the electrodes which stops the decomposition reactions but is still permeable to the Li+ cations which are the charge carriers At the graphite anode this film is commonly referred to as a solid electrolyte interphase SEI Aprotic organic compounds containing vinylene groups can form an effective SEI on a graphitic anode As examples vinyl acetate VA and acrylonitrile AN have been investigated by insitu Fourier transform infrared FTIR spectroscopy in a specially developed IR cell The measurements focus on electrolyte decomposition and the mechanism of SEI formation in the presence of VA and AN We conclude that cathodic reduction of the vinylene groups ie via reduction of the double bond in the electrolyte additives is the initiating and thus a most important step of the SEIformation process even in an electrolyte which contains only a few percent ie electrolyte additive amounts of the compound The possibility of electropolymerization of the vinylene monomers in the battery electrolytes used is critically discussed on the basis of the IR data obtainedFinancial support by the Austrian Science Fund FWF through the “Electroactive Materials” special research program is gratefully acknowledged We would like to thank Mitsubishi Chemical Corp Tsukuba Research Center Japan Honeywell Seelze Germany Merck Darmstadt Germany and TIMCAL Group Bodio Switzerland for supplying samples used in this study
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