Analysis of Lithiation and Delithiation Kinetics in Silicon

TL;DR

This paper investigates the kinetics of lithiation and delithiation in crystalline silicon electrodes using a model based on Tafel kinetics, providing insights into reaction parameters and their impact on electrode behavior.

Contribution

It introduces a methodology to estimate kinetic parameters and side-reaction rates in silicon electrodes, enhancing understanding of lithiation/delithiation mechanisms.

Findings

Estimated kinetic parameters are consistent across different silicon electrode states.

Large potential offsets are partly due to small exchange current densities.

The model accurately predicts electrode behavior during galvanostatic cycling.

Abstract

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 (i0/Cdl) 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 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 i0). Using the estimated parameters, the model is shown to predict successfully the behavior of the system under galvanostatic lithiation and delithiation.