Thermodynamic Factor for Facilitating Homogeneous Dendrite Growth in Alkali Metal Batteries

Abstract

This study suggests a critical factor that regulates (in)homogeneous growth based on an in-depth understanding of three alkali metal ((AM): Li, Na, and K) models using unified-multiscale atomistic calculations. The importance of AM disordered phases as a transition state is covered with a thermodynamic energy dataset using density functional theory (DFT) calculations, which indicates that the disordered-phase energy level (DPEL) plays a decisive role in controlling the degree of non-homogeneity during electrochemical deposition. Using the DFT-assisted machine learning method, the DPEL-related cohesive energy is investigated to understand in depth the energy level of disordered phase. Reliable molecular dynamics (MD) simulations systematically compare AM growth during charging. The results illustrate severely fluctuating morphologies including sharp tips in Li metal, whereas Na and K metals showed smooth surfaces. Finally, the transition state thermodynamics are explored using cross-sectional AM growth models. Metallic Li is preferentially adsorbed on its crystalline phase rather than on grain boundaries comprising disordered phases, resulting in severe dendritic Li growth. However, these characteristics are rarely observed for K metal during the entire deposition process. Based on the growth mechanisms of the three types of AM models, DPEL poses a potentially universal design strategy for facilitating homogeneous lithium-metal dendrite growth.