All-solid-state batteries (ASSBs) are considered promising candidates for next-generation batteries due to their excellent safety performance guaranteed by inorganic solid electrolytes (SEs) with the non-flammability nature, as well as the greatly increased energy density enabled by the adoption of lithium metal anode. Unlike conventional lithium-ion batteries (LIBs) using liquid electrolytes, all the components within the ASSBs system, including the composite cathode, lithium anode, and solid electrolyte, are solid-state. Solid-solid interfacial contacts within ASSBs, such as the dendrite-electrolyte interface and electrode-electrolyte interface, are the origin of interfacial instability issues. The interfacial instability problems mainly exhibit in the form of lithium dendrite growth-induced short circuits and interfacial debonding failure inside composite cathode, which are the major hurdles on the road towards the large-scale commercialization of ASSBs. Experimental characterizations are limited by the coupling of the solid nature of SE (vision overlap), and ultrasmall length scale. Therefore, versatile and physics-based models to describe the electrochemical behaviors of the ASSBs are in pressing need.
Herein, considering the highly multiphysics nature of ASSB behaviors, fully coupled electrochemo-mechanics models at different scales are developed to investigate the underlying mechanism of dendrite growth and interfacial failure. From the energy conservation perspective, the electrochemical-mechanical phase-field model at the electrolyte scale is firstly established to explore the dendrite growth behavior in polycrystalline SE. The newly formed crack and the grain boundary are found to be the preferential dendrite growth paths, and stacking pressure affects the driving force for both dendrite growth and crack propagation. Next, the cell-scale multiphysics modeling framework integrating the battery model, mechanical model, phase-field model, and short-circuit model is developed to study the entire process from battery charging to dendrite growth and to the final short circuit. The governing effects from various dominant factors are comprehensively discussed. Further on, inspired by the “brick-and-mortar” structure, the strategy of inserting heterogeneous blocks into SEs is proposed to mitigate dendrite penetration-induced short circuit risk, and the overall dendrite mitigation mechanism map is given. Finally, the three-dimensional fully coupled electrochemical-mechanical model is developed to investigate the interfacial failure phenomena, taking into account the electrochemical reaction kinetics, Li diffusion within the particle, mechanical deformation, and interfacial debonding. The randomly distributed LiNi1/3Co1/3Mn1/3O2 primary particles result in the anisotropic Li diffusion and volume variation inside the secondary particle, leading to significant nonuniformity of the Li concentration, strain, and stress distributions. This also serves as a root cause for the internal cracks or particle pulverization. The particle volume shrinkage under the constraint of the surrounding SE triggers the interfacial debonding with increased interfacial impedance to degrade cell capacity. This study explores the dendritic issue and mechanical instability inside ASSBs from the multiphysics perspective at different scales, obtaining an in-depth understanding of the electrochemical-mechanical coupling nature as well as providing insightful mechanistic design guidance maps for robust and safe ASSB cells.