A Multi-Scale Electrochemical Modeling of Amorphous Silicon Thin Film in a Lithium Ion Batteries

The electrochemical performance of Li-ion batteries strongly depends on the interaction between atomic scale and micro scale phenomena in particular, within the electrodes. Therefore, we propose a multi-scale model to characterize the electrochemical and mechanical response of amorphous silicon thin film with discharge-charge cycling.In multiscale frameworks, we analyze the lithium kinetics and the thermodynamics such as lithium migration energy barriers and excess gibsss free energy of lithium silicon alloys using density functional theory calculation. With the calculated results, the lithiation behavior in silicon thin film anode shows the large deviation compared to the simulated results based on an ideal solution model. We identify that these effects account for nonlinear lithium diffusion behavior using continuum based numerical simulation. We also consider the coupled diffusion and mechanical model for the cell scale,and determine non equilibrium cell potential as function of surface lithium concentration using Bulter-Volmer kinetics. Our simulation results are shown to be well consistent with known experimental observation at different C-rates and thicknesses.This multi-scale approach in lithium ion battery can provide essential guidance in the interpretation of lithiation and delithiation phenomena and is enable of predicting battery performance before experiments are ever performed.