Fundamental Understanding of Solid Electrolyte Interface (SEI) Effects on Li Dendrite Evolution: Multi-Scale Modeling Study
Authors: Yurkiv Vitaliy , Ramasubramanian Ajaykrishna , Foroozan Tara , Shahbazian-Yassar Reza , Mashayek Farzad 
Published: February 2020

Safety concerns of lithium (Li) metal battery (LMB) originated from Li dendrite formation, and the resulting internal electric short circuit have become the major obstacle for successful practical usage of LMB. Significant research has been conducted to understand the mechanisms of dendritic growth of Li, and develop strategies to prevent the Li dendrite formation1; however, the progress has been limited due to the lack of fundamental understanding of the solid electrolyte interface (SEI) influence on the dendrite formation and growth.

In this work, we present the modeling results of Li dendrite formation and growth based upon an extended phase-field model (PFM) for Li electrodeposition, atomisticlly informed by the density functional theory (DFT) calculation. The PFM2 is developed employing MOOSE framework 3, based on the work of Guyer et al.4,5 and Bazant6 on the topic of phase-field modeling of electrodeposition. The SEI model is based upon the grain boundary (GB) model7 considering the Li-ions diffusion across the GB. Utilizing DFT calculation, we could successfully obtain the anisotropic strength of the Li dendrites, the energy of Li nucleation and the Li+ diffusion coefficient across the SEI. Subsequently, the thermodynamically consistent free energy density and the gradient energy coefficient, which is modeled by taking into account the surface energy anisotropy, are used in the PFM to predict the spatiotemporal evolution of Li dendrites in the presence of SEI.

We investigate three regimes of Li dendrite growth, such as Li filaments evolution, Li bush-like structure evolution and the transition between Li filaments and bush-like morphologies. The Li filaments nucleation and growth is more straightforward, with clear dependency on Li+ and potential distribution. The Li bush-like structure evolution is more complicated, where the electric potential distribution and Li+ flux profile reveal relatively complex nonlinear influence on the Li electrodeposition. Thus, the present study, in addition to improving the fidelity of the PFM of Li electrodeposition, identifies critical regimes of Li filaments growth and splitting, allowing for a more profound understanding of the SEI influence on Li dendrite evolution. Based upon this work, the development of strategies towards prevention of Li dendrites formation for long-lasting, high-density LMB will be facilitated.

References:

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