Insights into the Anode-Initiated and Grain Boundary-Initiated Mechanisms for Dendrite Formation in All-Solid-State Lithium Metal Batteries

The formation of lithium dendrites severely hinders the practical application of all-solid-state lithium metal batteries (ASSLMBs). The conventional view is that dendrites initiate at the anode and then grow into solid electrolytes (SEs), while a recent popular opinion holds that Li+ ions can directly be reduced at grain boundaries (GBs) within electrolytes, and these internal dendrites then interconnect resulting in the short-circuit failure. However, whether the internal GBs or the anode interface dominates the dendrite initiation is still under debate. Herein, first-principles calculations on the representative system, Li6PS5Cl (LPSC), are performed to investigate these two dendrite initiation mechanisms. The results show that the solid electrolyte interphase (SEI) blocks the electron leakage, making the internal Li+ ions less likely to deposit. Combining ab initio molecular dynamics (AIMD) simulations with theoretical models, the critical current density (CCD) for dendrite formation at the anode interface is predicted to be much lower than at the GBs, indicating dendrites are easier to initiate at the anode. This study reveals that the dendrite formation is governed by the anode-initiated mechanism instead of the GB-initiated one. These findings suggest that the anode interface should be a primary concern for designing dendrite-free batteries rather than the GBs.