A review of doping strategy for rapid Li + migration in the stable lithium lanthanum zirconate solid electrolytes

Abstract Given the safety concerns and low energy density induced by liquid electrolytes, the interest in solid‐state lithium metal batteries is rapidly growing. Among various solid electrolytes, garnet‐type lithium lanthanum zirconate (LLZO) has attracted extensive attention due to its numerous advantages. This review systematically summarizes the intrinsic issues faced by unstable bare LLZO and the resolution strategy of metallic doping in the electrochemical application. It comprehensively discusses the doping arrangements for high ionic conductivity based on element types and gap filling using second phases/sintering aids for LLZO grains/pellets. Emphasizing diverse doping strategies for bulk LLZO, it relates to simulation and characterization findings along with novel synthesis approaches. By identifying the inherent scientific questions of LLZO, this review bridges the long‐existing gaps between the doping strategy guidelines for suitable crystalline phase and the surge of high Li + conductivity for practical solid‐state lithium batteries.