Simulation and Experiment on Solid Electrolyte Interphase (SEI) Morphology Evolution and Lithium-Ion Diffusion

In this study, a phase-field model is developed to simulate the microstructure morphology evolution that occurs during solid electrolyte interphase (SET) growth. Compared with other simulation methodologies, the phase-field method has been widely applied in the solidification modeling that has great relevance to SET formation. The developed model can simulate SET structure and morphology evolution, and can predict SET thickness growth rate. X-ray photoelectron spectroscopy (XPS) experiments are performed to confirm the major SET species as LiF, Li2O, ROLi, and ROCO2Li. Transmission electron microscopy (TEM) experiment is performed to present the SET layer structures. The experiments reduce the complexity of the model development and provide validation to some extent. Fick's law and mass balance are applied to investigate lithium-ion concentration distributions and diffusion coefficients in different types of SEI layers predicted by the phase-field simulations. Simulation results show that lithium-ion diffusion coefficients between 298 K and 318K are 1.340-7.328(10(-16)) cm(2)/s, 1.734-3.405(10(-12)) cm(2)/s, and 2.611-2.389(10(-15)) cm(2)/s in the compact, porous, and multilayered structures of SET layer, respectively. The resistances between 298 K and 318 K are 0.740-1.693 Omega.cm(2), 2.827-5.517 Omega.cm(2), and 3.726-5.839 Omega.cm(2) in the compact, porous, and multilayered structures of SET layer, respectively. (C) The Author(s) 2015. Published by ECS. All rights reserved.