Effect of Stress and Surface Roughness on Electrodeposition in All-Solid-State Batteries: A Computational Investigation
All-solid-state batteries (ASSBs) promise high energy density and enhanced safety, but their development is hindered by instability and incompatibility at solid-solid interfaces. In Li-metal ASSBs, lithium penetration occurs despite stiff ceramic electrolytes via grain boundaries, often initiated by minor Li/SE interfacial irregularities. Here we introduce a two-dimensional continuum model with electro-chemo-mechanical coupling to investigate interfacial current distribution in Li ASSBs with surface-roughened argyrodite electrolyte under stack pressures and applied current density. Our theoretical analysis and simulation studies highlight the critical role of mechanical stress in interfacial current distribution. We find that prominent stress variations around elongated surface protrusions are the key to nonuniform Li deposition, without which Li deposition becomes uniform even on a rough surface. Moreover, our parametric study elucidates that stress effects dominate the overpotential and current distribution under low interfacial current density to exchange current density ratios, otherwise the high interfacial resistance due to surface-roughness-induced interfacial area becomes dominant. With these insights, we also discuss the potential of engineering artificial interlayers to modulate interfacial current distributions, offering guidance for improving the long-term performance and reliability of ASSBs.