(Invited) Atomically-Informed Phase-field Modeling of Li and Mg Electrodeposition Morphologies

Abstract

Exploring the origin of non-dendritic Mg electrodeposition might provide a new prospect of realizing the Li metal anode application in next-generation batteries. To fundamentally understand the morphological difference between Li and Mg plating, we hereby developed a multiscale model for a general metal electrodeposition process based on the phase-field method and transition state theory, connecting the atomic level charge-transfer physics to the mesoscale morphological evolution. At the atomic level, density functional theory (DFT) based half-cell calculations were used to predict the interfacial structures, de-solvation processes and Li+/Mg2+ ion energy landscapes at Li/SEI/ethylene carbonate (EC)-electrolyte and Mg/ tetrahydrofuran(THF)-electrolyte, and the effects of electric field on them. With thermodynamic and kinetic parametric inputs from DFT calculation (i.e. interfacial energy and anisotropy of Li/SEI (Li2CO3), surface energy and anisotropy of Mg, diffusion coefficient of Li+ in SEI (Li2CO3), and relative difference in charge-transfer energy barrier of Li/Mg plating), our non-linear phase-field model captures the morphological evolution difference between dendritic Li plating and faceted Mg plating. Furthermore, through systematical parametric analyses, we conclude that the cation desolvation-induced exchange current difference between Li and Mg is mainly responsible for their deposition morphological differences. This study provides a strategy of connecting the phase-field method and atomistic calculations and sheds lights on the dendrite-free battery anode design.