Effects of LLZO Microstructure Porosity, LLZO/Li‐Metal Interfacial Polarization Resistance, and Applied Areal Current Density on Li‐Metal Dendrite Formation in LLZO Bilayer Symmetric Cells

ABSTRACT Idealized Li‐Li symmetric cells utilizing porous‐dense Li 7 La 3 Zr 2 O 12 (LLZO) “bilayers” are simulated to characterize the risks for “interfacial” and “internal” Li‐metal dendrite formation and provide insight for bilayer full cells. The higher interfacial area of the porous LLZO/Li‐metal interface decreases the interfacial overpotentials and increases the Critical Current Density (CCD) for interfacial dendrites. Decreasing the polarization resistance ( ASR polar ) of the LLZO/Li‐metal interface further increases the CCD for interfacial dendrites. Simultaneously, tortuous transport paths through the porous LLZO layer amplify the local ionic current densities, thereby increasing the risk of internal dendrite formation if internal defects/pores are present. Decreasing the ASR polar value, the microstructure porosity of the porous LLZO layer, or the applied areal current density all decrease the risk for internal dendrites. If interfacial dendrites have the lowest CCD, the microstructure porosity in a bilayer full cell may be increased to increase the Li‐metal anode areal capacity with minimal effect on the interfacial CCD. If internal dendrites have the lowest CCD, the bilayer full cell design should be tailored to the operating conditions, with higher microstructure porosity utilized for lower cycling rates and high energy density applications, and lower microstructure porosity utilized for higher cycling rates and high power density applications.