Model Based Multiscale Analysis of Film Formation in Lithium-Ion Batteries

Evidence for multiscale interaction of processes during surface film growth is provided using a multiscale modeling approach. The model directly couples a continuum pseudo two dimensional (P2D) battery model and a heterogeneous surface film growth model based on the kinetic Monte Carlo (kMC) method. Key parameters have been identified at basic electrochemical experiments, i. e., open circuit potential (OCP), C-rate tests, and potential during filmformation. Simulations are in very good agreement with these experiments. Simulation results are shown for various formation procedures, i. e., for different applied C-rates. Interaction between macroscopic transport processes on electrode scale and elementary reaction steps on atomistic scale are observed. Results reveal a distinct impact of the applied procedures on the atomistic structure of surface films. It can be seen that locally heterogeneous films are formed with very slow charging rate due to stochasticity of the growth process, while spatially heterogeneous films are formed with very fast charging rate due to the spatial heterogeneous distribution of concentration and potential. Therefore, the author's emphasize that in order to identify charging protocols for optimal film morphology multiscale interactions should be considered.