Interface Challenges and Engineering Strategies in Sulfide Solid Electrolyte-Based All-Solid-State Lithium–Sulfur Batteries

Abstract

All-solid-state lithium–sulfur batteries (ASSLSBs) combine sulfur's theoretical specific capacity of 1675 mA h g -1 with the safety potential of nonvolatile solid electrolytes. By eliminating the liquid dissolution–diffusion medium, sulfide solid electrolytes (sulfide SSEs) suppress conventional polysulfide migration while retaining high room-temperature Li-ion conductivity and favorable processability. This replacement, however, converts a liquid-wetted porous electrode into a pressed solid assembly in which sulfur conversion depends on real contact and coupled ion/electron transport. Chemical failure arises from sluggish S 8 /Li 2 S conversion and oxidative or reductive decomposition of sulfide SSEs, whereas physical failure arises from dynamic three-phase-contact loss, conversion strain, through-thickness reaction gradients, stripping voids, and lithium penetration. This focused perspective examines selected primary studies through an evidence-normalization lens, distinguishing direct observations from cross-study inference under explicit capacity bases and test boundaries. Across these studies, stable cycling is associated with selective interfacial chemistry, continuous ionic/electronic pathways, and sustainable mechanical contact; neither high bulk ionic conductivity nor high stack pressure alone removes interfacial failure. Practical comparisons should report loading, current, temperature, pressure, electrolyte thickness, and inactive-component inventory together with gravimetric performance. This perspective separates mechanistic evidence from metrics inflated by low loading, elevated temperature, or reversible non-sulfur charge storage.