Enhancing ionic conductivity in Li₇P₃S₁₁ solid electrolytes via doping strategies: Implications for solid-state lithium-sulfur batteries

Solid-state electrolytes in the Li₂S-P₂S₅ system have emerged as promising candidates for next-generation all-solid-state batteries (ASSBs) due to their high ionic conductivity and superior electrochemical stability. Among these, the Li₇P₃S₁₁ phase exhibits exceptional ionic conductivity (∼10⁻³ S cm⁻¹ at room temperature), making it a focal point for materials research. This review provides a comprehensive analysis of dopant-driven modifications in Li₇P₃S₁₁, emphasizing their impact on structural evolution, ionic transport, electrochemical performance, and long-term stability. Both cationic (e.g., transition and alkali metals) and anionic (e.g., oxygen) doping strategies are examined, offering insights into their roles in optimizing ionic conductivity and interfacial compatibility. Sulfide dopants enhance lithium-ion mobility and interfacial stability with lithium metal and sulfur cathodes, while oxide dopants improve air stability and suppress dendrite formation. Nitride dopants, though beneficial for interfacial compatibility, may introduce additional resistance at electrode-electrolyte interfaces. Despite these advancements, challenges such as dopant-induced phase instability, synthesis complexity, and environmental sensitivity persist, necessitating a strategic approach to doping. By categorizing dopants based on their chemical interactions with the Li₇P₃S₁₁ matrix, this review outlines a framework for rational dopant selection and design. The insights presented herein provide a foundation for advancing doped solid electrolytes, accelerating the development of high-performance lithium‑sulfur batteries for next-generation energy storage applications.