Fracture Dynamics\nin Silicon Anode Solid-State Batteries

Solid-state batteries (SSBs) with silicon anodes could\nenable improved\nsafety and energy density compared to lithium-ion batteries. However,\ndegradation arising from the massive volumetric changes of silicon\nanodes during cycling is not well understood in solid-state systems.\nHere, we use <i>operando</i> X-ray computed microtomography\nto reveal micro- to macro-scale chemo-mechanical degradation processes\nof silicon anodes in SSBs. Mud-type channel cracks driven by biaxial\ntensile stress form across the electrode during delithiation. We also\nfind detrimental cracks at the silicon/solid electrolyte interface\nthat form due to local reaction competition between neighboring domains\nof different sizes. Continuum phase-field damage modeling quantifies\nstress-driven channel cracking and shows that the lithiated silicon\nstress state is critical for determining the extent of interfacial\nfracture. This work reveals the mechanisms that govern SSBs compared\nto conventional lithium-ion batteries and provides guidelines for\nengineering chemo-mechanically resilient electrodes for high-energy\nbatteries.