Atomistic Mechanisms Underlying the Maximum in Diffusivity in Doped Li₇La₃Zr₂O₁₂

Doped lithium lanthanum zirconium oxide (LLZO) is a promising class of solid electrolytes for lithium-ion batteries due to their good electrochemical stability and compatibility with Li metal anodes. Ionic diffusivity in these ceramics known occur via correlated, vacancy-mediated jumps Li+ between alternating tetrahedral octahedral sites. Aliovalent doping at the Zr site increases concentration vacancies sublattice cation diffusivity, but such an increase universally followed by decrease lower than 6.3–6.5 molar content. Molecular dynamics simulations based on density functional theory show that maximum originates from competing effects increased vacancy increasing occupancy low-energy sites Li+, which overall activation energy associated diffusion. For relatively high temperatures our simulations, plays dominant role transport as compared dopant chemistry.