Garnet‐Type Solid‐State Electrolytes: Crystal‐Phase Regulation and Interface Modification for Enhanced Lithium Metal Batteries

Abstract Due to their substantial energy density, rapid charging and discharging rates, and extended lifespan, lithium‐ion batteries have attained broad application across various industries. However, their limited theoretical capacity struggles to meet the growing demand for battery capacity in consumer electronics, automotive, and aerospace applications. As a promising substitute, solid‐state lithium‐metal batteries (SSLBs) have emerged, utilizing a lithium‐metal anode that boasts a significant theoretical specific capacity and non‐flammable solid‐state electrolytes (SSEs) to address energy density limitations and safety concerns. For SSLBs to attain large‐scale commercial viability, SSEs require heightened ionic‐conductivity, improved mechanical characteristics, and enhanced chemical and electrochemical stability. Furthermore, tackling the challenges related to interfacial contacts between SSEs and the lithium‐metal anode is imperative. This review comprehensively overviews the primary methods used to prepare garnet SSEs and summarizes doping strategies for various sites on Li 7 La 3 Zr 2 O 12 (LLZO) garnet SSEs, aiming to optimize the crystal phase to achieve more favorable properties in SSE applications. Additionally, it discusses strategies for modifying the interfacial contact between the lithium‐metal anode and SSEs, classifying them into three areas: surface modification, interlayer‐modification, and composite anodes. This review aims to serve as a valuable reference for future researchers working on high‐performance garnet SSEs and effective interfacial‐modification strategies.