Formation and growth of surface films on graphitic anode materials for Li-ion batteries

The inductive loop observed in the impedance spectra of the graphite electrode in Li/C cells is attributed to the formation of a (Li1-XC6)/C-6 concentration cell from which current flows in opposition to Li intercalation into graphite, consistent with the conditions for the generation of an inductive loop. The current flow occurs in the (Li1-XC6)/C-6 concentration cell because of the leaky nature of the solid electrolyte interphase (SEI) that isolates Li-rich and Li-deficient islands of carbon or graphite in the electrode during the SEI's formation stage. An equivalent circuit model has been proposed that fits the experimental data well. (C) 2005 The Electrochemical Society.