Dynamic interplay of dendrite growth and cracking in lithium metal solid-state batteries

All-solid-state batteries (ASSBs) represent a significant leap forward compared to conventional liquid-electrolyte based batteries, offering enhanced energy density, improved safety, extended cycle longevity, and reduced environmental footprint. However, the persistent challenge of uncontrollable dendrite growth within solid electrolytes (SEs) has posed substantial obstacles to the realization of Li metal ASSBs. This study develops a phase field model to unveil a dynamic interplay between Li dendrite growth and crack propagation in the polycrystalline Li₇La₃Zr₂O₁₂ (LLZO) solid electrolyte. Our modeling highlights distinct nucleation sites for Li electrodeposition, localized in proximity to the electrode/SE interface, a phenomenon sensitive to cell geometry. Li deposition initiates local stress accumulation that wedges the SE to cracking, and fracture induced stress relaxation facilitates further Li electrodeposition. Remarkably, a reciprocal relationship emerges between Li dendrite growth and crack propagation, each process reinforcing the other in an alternating manner. The dynamic interplay unveils a characteristic “wait-and-go” temporal sequence, where the progression of Li dendrites consistently trails behind the crack tip, aligning with the previous experimental observations. Drawing from the reciprocal dynamics, we identify practical stress-engineering strategies to mitigate catastrophic cell failure by simultaneously retarding Li dendrite growth and redirecting the crack propagation paths. Our findings offer electrochemo-mechanical insights in cell design and stress management, thereby opening a unique pathway towards the realization of safe and durable Li metal ASSBs.