The irreversible capacities caused by the reduction of solvent on the surface of a negative electrode (KMFC:
Kawasaki Mesophase Fine Carbon) were examined during the initial cycle in ethylene carbonate (EC)-diethyl
carbonate (DEC) electrolyte solutions at various concentrations of LiPF6. Chronopotentiograms, linear sweep
voltammograms, and impedance spectra clearly showed differences in irreversible capacity and that those differences
are related to the concentration of electrolyte during the initial charge. These differences were caused
by the amount of solvent decomposition as a function of the concentration of LiPF6 electrolytic salt. The data
are discussed with reference to the concentration of electrolytic salt and the properties of passivation film
formed by solvent decomposition.
Keywords : Passivation film, Lithium ion battery.
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