Recent development of lithium argyrodite solid-state electrolytes for solid-state batteries: Synthesis, structure, stability and dynamics

Solid electrolyte plays a key role to enable good safety reliability and high performance of all-solid-state lithium batteries. Among the diverse solid electrolytes, argyrodites represent a relatively new and promising class of sulfide-based lithium-ion superconductors due to their high ionic conductivity at room temperature, low cost and good compatibility towards Li metal. However, lithium argyrodites remain challenging for practical applications despites of the continuous improvements from research. Herein, we review the recent research advancements and limitations of lithium argyrodites from material to battery level. Material synthesis based on solid and liquid routes are summarized. The chemical structures of lithium argyrodites, their lithium-ion transport mechanism and various optimization strategies for high ionic conductivity are discussed. The chemical and electrochemical stabilities of lithium argyrodites towards cathode and anode materials and corresponding improvement approaches are discussed in detail. The perspectives on future research directions of lithium argyrodites are provided.