Analysis of Electrochemical Lithiation and Delithiation Kinetics in Silicon

Analysis of lithiation and delithiation kinetics in pulse-laser-deposited\ncrystalline thin-film silicon (Si) electrodes is presented. Data from\nopen-circuit relaxation experiments are used in conjunction with a model based\non Tafel kinetics and double-layer capacitance to estimate the apparent\ntransfer coefficients ({\\alpha}a, {\\alpha}c), and exchange current density to\ncapacitance ratio (i0/Cdl) for lithiation and delithiation reactions in a\nlithiated silicon (LixSi) system. Parameters estimated from data sets obtained\nduring first-cycle amorphization of crystalline Si, as well as from cycled\ncrystalline Si and amorphous Si thin-film electrodes do not show much\nvariation, indicating that they are intrinsic to lithiation/delithiation in Si.\nA methodology to estimate the side-reaction rate and its role in the evolution\nof the open-circuit potential of the LixSi system are discussed. We conclude\nthat the large potential offset between lithiation and delithiation reactions\nat any given state of charge is partially caused by a large kinetic resistance\n(i.e., small i0). Using the estimated parameters, the model is shown to predict\nsuccessfully the behavior of the system under galvanostatic lithiation and\ndelithiation.\n