How Grain Boundaries Impede Lithium-Ion Diffusion and Induce Dendrite Growth: Insights from First-Principle Calculations and Deep Potential Molecular Dynamic Simulations

The presence of grain boundaries (GBs) in solid-state electrolytes is believed to impede ion transport and induce dendritic growth. However, traditional experimental and theoretical methods have limitations in exploring the atomic details of ion diffusion and dendrite growth in the GB region. Herein, we combined deep potential molecular dynamics (DPMD) simulations with density functional theory (DFT) calculations to explore the underlying causes of some harmful phenomena induced by GBs. DFT calculations and DPMD simulations reveal that due to the abundant defects and strong reducibility of the GB regions, ions and electrons are easily trapped and accumulate in the GB regions. The accumulation of ions and electrons not only impedes ion diffusion in the bulk region but also elevates the probability of Li ion reduction into metallic Li, which may induce dendrite growth.