Modeling of lithium electrodeposition at the lithium/ceramic electrolyte interface: The role of interfacial resistance and surface defects

Inorganic solid electrolytes, paired with Li-metal anodes, could result in high energy density yet safe rechargeable lithium batteries. To enable Li-metal anodes, the ceramic separator needs to be mechanically robust to occlude the path for Li-dendrites growth and prevent cell shorting. Using a continuum model, we explore the role of surface geometry and interfacial resistance on Li deposition. The model calculates the intensification of the cathodic current due to crack-like defects on the electrolyte surface. The driving force for plating at the crack tip increases with the crack length. As the crack grows the current at its tip grows, making the system unstable. However, due to the stress-potential coupling, the plating rate decays as the pressure rises in the Li-filament inside the crack. High interfacial resistance leads to more uniform plating but it also causes high overpotentials. A larger stress is required to compensate such overpotentials and stop plating at the crack tip. If the pressure at the crack tip overcomes the fracture toughness of the electrolyte material the defect propagates across the separator. Our results show that controlling the lithium-electrolyte interfacial properties, such as defect size and interfacial resistance, is critical for solid-state battery durability and charging performance.