Kinetic characterization of the electrochemical intercalation of lithium ions into graphite electrodes

Lithium intercalated graphites have taken the place of metallic lithium as anodes for secondary lithium batteries. Controlling the anode-electrolyte i nterface has been a major technical challenge in the development of lithium -ion battery technologies. The interfacial characteristics can be greatly a ffected by the kinetics of intercalation. However, the kinetics of the elec trochemical intercalation of lithium into graphites has not been well analy zed yet. Very few kinetic and interfacial parameters have been reported. In this work, the electrochemical impedance spectroscopy, constant charge ste p, and galvanostatic pulse polarization techniques were applied to study th e kinetics of the intercalation and deintercalation processes of graphite e lectrodes in a few important lithium battery electrolyte solutions. Based o n the proposed equivalent circuit model, we determined the kinetic and inte rfacial parameters of the intercalation and deintercalation processes. The measured intercalation charge-transfer resistance, exchange current densiti es. and intercalation capacitance range between 11 and 28 Omega cm(2), 1.0 and 2.3 mA/cm(2), and 1.0 and 2.0 mu F/cm(2), respectively, depending on th e electrolyte solution compositions. The dependence of these kinetic and in terfacial parameters on solvent composition, electrolyte concentration, sto rage time, and intercalated state is discussed. In addition, the transfer c oefficients have been determined. The results suggest that the intercalatio n/deintercalation process is electrochemically reversible. (C) 2000 The Ele ctrochemical Society. S0013-4651(99)11-022-X. All rights reserved.