Intercalation of Lithium Ions into Graphite Electrodes Studied by AC Impedance Measurements

Effects of electrolyte concentrations and the level of preintercalation ( x values in ) on the lithium ion intercalation into graphite lattices have been examined in propylene carbonate‐ethylene carbonate mixed solutions with as an electrolyte by ac impedance measurement techniques. Exchange current densities were determined for reductive intercalation of lithium by ac impedance measurements to range between 1.4 and depending on the amount of intercalated lithium ions with a transfer coefficient (α) of 0.65. Diffusion coefficients during the deintercalation process have also been determined at various preintercalation levels. The dependence of diffusion coefficients and exchange currents on the x values in ( ≤ 1) is discussed. © 1999 The Electrochemical Society. All rights reserved.