Research Advances in Rare‐Earth‐Based Solid Electrolytes for All‐Solid‐State Batteries

All-solid-state batteries (ASSBs) and solid-state electrolytes (SSE) have emerged as promising alternative energy storage devices for traditional lithium-ion batteries, drawing significant attention from researchers. Notably, SSE materials incorporating rare earth elements have demonstrated remarkable advancements in terms of ionic conductivity, electrochemical stability, and cycle-reversible performance. The unique electron layer structures of rare earth elements facilitate diverse energy level transitions. Meanwhile, their relatively large ionic radius contributes to excellent ionic conductivity, mechanical strength, and electrochemical properties in the electrolyte. This paper offers a comprehensive review of rare-earth-based oxide solid electrolytes, rare-earth-based sulfide solid electrolytes, rare-earth-based halide solid electrolytes, and composite polymer electrolytes enriched with rare earth elements. The characteristics, applications, modification methods, and underlying mechanisms of these SSE materials are investigated, offering valuable insights and inspiration for the design of future SSE materials. Additionally, this paper systematically presents solutions for improving the performance of ASSBs and explores the ion transmission in these batteries. Finally, the research direction, optimization methods, and development prospects of rare-earth-based solid electrolytes are analyzed and forecasted.