Diagnostic characterization of high power lithium-ion batteries for use inhybrid electric vehicles

A baseline cell chemistry was identified as a carbon anode, LiNi0.8Co0.2O2 cathode, and diethyl carbonate-ethylene carbonate LiPF6 electrolyte, and de signed for high power applications. Nine 18650-size advanced technology dev elopment cells were tested under a variety of conditions. Selected diagnost ic techniques such as synchrotron infrared microscopy, Raman spectroscopy, scanning electronic microscopy, atomic force microscopy, gas chromatography , etc., were used to characterize the anode, cathode, current collectors an d electrolyte taken from these cells. The diagnostic results suggest that t he four factors that contribute to the cell power loss are solid electrolyt e interphase deterioration and nonuniformity on the anode; morphology chang es, increase of impedance, and phase separation on the cathode; pitting cor rosion on the cathode current collector; and decomposition of the LiPF6 sal t in the electrolyte at elevated temperature. (C) 2001 The Electrochemical Society.