All-solid-state battery safety in abnormal thermal situations: Crack propagation and lithium dendrite growth

Battery safety problems in abnormal thermal situations such as operation in cold/hot environment, thermal management defunction and thermal runaway attract addressing attentions. Here from the battery safety perspective, a coupled thermal-electrochemical-mechanical phase-field model is developed for crack propagation and lithium dendrite growth, thus to illustrate the underlying mechanisms of interfacial failure and dendrite evolution in lithium metal all-solid-state batteries (ASSBs) under abnormal thermal situations. The effects of inter-cell temperature distribution direction and magnitude, stacking pressure, and interfacial roughness at on crack propagation and dendrite growth are systematically investigated. Originating from augmented strain energy density by thermal expansion, crack propagation is much accelerated at negative temperature differences (NTD), which provide more space for dendritic growth as well as inducing stronger longitudinal evolution directionality. The fastest dendrite distance at NTD increases much faster than that under positive temperature difference (PTD) for significantly enhanced electrochemical driving force. Under isothermal or PTD conditions, an applied stacking pressure below than 30 MPa can inhibit the crack propagation and fastest dendrite evolution. However, at NTD, any applied stacking pressure contributes to crack propagation and lithium dendrite growth. More initial defects increase the crack region area, meanwhile the crack propagation depth is shortened due to weakened von Mises stress and strain energy density. Considering both crack propagation and fastest dendrite evolution, applying a suitable stacking pressure below 10 MPa to improve the Li/solid electrolyte (SE) interface is desired, thus to reduce the interfacial failure and possibility of short circle. The findings offer an alternative comprehensive perspective to evaluate the battery safety under abnormal thermal conditions, and could provide rational guidance for design and development highly reliable ASSBs.