Analysis of Electrochemical Lithiation and Delithiation Kinetics in Silicon

Analysis of lithiation and delithiation kinetics in pulse-laser-deposited crystalline thin-film silicon (Si) electrodes is presented. Data from open-circuit relaxation experiments are used in conjunction with a model based on Tafel kinetics and double-layer capacitance to estimate the apparent transfer coefficients (alpha(a), alpha(c)) and exchange current density to capacitance ratio (i(0)/C-dl) for lithiation and delithiation reactions in a lithiated silicon (LixSi) system. Parameters estimated from data sets obtained during first-cycle amorphization of crystalline Si, as well as from cycled crystalline Si and amorphous Si thin-film electrodes do not show much variation, indicating that they are intrinsic to lithiation/delithiation in Si. A methodology to estimate the side-reaction rate on a well-cycled electrode and its role in the evolution of the open-circuit potential of the LixSi system are discussed. We conclude that the large potential offset between lithiation and delithiation reactions at any given state of charge is partially caused by a large kinetic resistance (i.e., small i(0)). Using the estimated parameters, the model is shown to predict successfully the behavior of the system under galvanostatic lithiation and delithiation. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.008303jes] All rights reserved.