Sulfide Solid Electrolytes for All-Solid-State Batteries: Electrochemical Properties, Ion Transport Mechanisms, and Performance Correlations

Abstract

Because of their high ionic conductivity, sulfide solid electrolytes have emerged as important contenders for all-solid-state battery technology, which is a potential future technology delivering enhanced energy efficiency and security. Sulfide-based solid electrolytes including glassy, glass-ceramic, and crystalline forms display a broad spectrum of ionic conductivity (~ 10⁻⁷ to 10⁻² S cm⁻¹) and activation energy (~0.12–0.60 eV), largely dictated by their composition, structural features, and phase characteristics. Glassy systems generally exhibit conductivity in the range of ~ 10⁻⁶ to 10⁻² S cm⁻¹ with activation energy of ~0.22–to 0.37 eV, where the introduction of halides and network modifiers plays a key role in enhancing Li⁺ transport. Glass-ceramic electrolytes offer improved performance (~ 10⁻⁴ to 10⁻² S cm⁻¹; ~0.12–0.34 eV), primarily due to the emergence of highly conductive phases such as Li₇P₃S₁₁ and increased structural disorder. Among all crystalline electrolytes, the LGPS-type and argyrodite families in particular achieve superior ionic conductivity (~10⁻² S cm⁻¹) with relatively low activation energy (~0.15–0.25 eV), owing to their well-defined Li⁺ conduction pathways. Overall, the evident inverse correlation between activation energy and ionic conductivity underscores the importance of compositional design and structural optimization, establishing doped sulfide electrolytes as promising candidates for advanced all-solid-state lithium battery technologies.