Extraction and Analysis of Electrolyte from Commercial Lithium ion Cells

摘要

Up till now numerous studies and diagnostic approaches have concentrated on investigating the lithium-ion cell electrolyte for changes induced by cycling or aging. However the preliminary step in any such investigations, that is the method of extracting the electrolyte from the lithium-ion cells, has been seldom addressed. The present work gives an insight into a simple and comprehensive procedure evolved for the collection of electrolyte sample from 18650 lithium-ion battery cells. The evolved procedure is easy to implement and ensures that the integrity of electrode assembly inside the cell is preserved intact during electrolyte extraction. Furthermore, the mode of processing the extracted electrolyte by liquid-liquid extraction using dichloromethane-water mixture, for suitability towards chromatography analyses has also been addressed in detail. The extracted and processed electrolyte samples from three 18650 COTS cells, namely, Panasonic (NCR 18650B), Samsung (ICR 18650-26F) and LG cell (DS2 18650) have been analyzed using Gas Chromatography and Mass Spectrometry method. Both the analyzed samples of Panasonic and Samsung have been inferred to consist of ethylmethylcarbonate and ethylenecarbonate solvents, whereas LG electrolyte sample has been understood to consist of diethylcarbonate and ethylenecarbonate.