Electrochemical-Mechanical Coupled Crack Propagation and Dendrite Growth in All-Solid-State Battery

Abstract

Lithium metal all-solid-state batteries (ASSBs) are considered as one of the most promising candidates for future lithium batteries thanks to their high safety performance and energy density. However, dendrite growth and interfacial issues induced failure and poor cyclability are the two fatal problems on the road of commercialization of ASSBs. To further understand the underlying mechanisms, coupled electrochemical-mechanical models for crack propagation and lithium dendrite growth are proposed from both the cell level and electrolyte level. From the cell level, we discover that the overpotential induced stress may drive the crack to penetrate the solid electrolyte and the dendrite growth eventually causes the short circuit. The short circuit occurs earlier with increasing charging rate and decreasing electrolyte conductivity. The effect of Young’s modulus on crack is expressed by affecting the driving force and the fracture energy. Larger fracture toughness represents higher threshold energy for crack, thus the dendrite growth speed is reduced. From the electrolyte level, we observe that longer defect with sharp edge causes more severe crack propagation and leads to larger dendrite growth area due to the increased strain energy density. The initial defect within grain plays an irrelevant role in the dendrite growth within the grain boundary. Stacking pressure greater than 10 MPa significantly speeds up crack propagation as well as dendrite growth due to the nontrivial mechanical driving force. Mechanical stress-induced strain-energy would contribute to more than 15% of the total dendrite growth once the stacking pressure exceeds 20 MPa, while it is trivial if the stacking pressure is below 10 MPa. Results provide a fundamental tool for the design and evaluation of ASSB safety and cyclability from a more comprehensive perspective and clear the barrier for the development of next-generation ASSBs.