Catalytic Solder Fuses Solid-Solid Interfaces for All-Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium-sulfur batteries (ASSLSBs) have garnered significant research interest due to their inherent safety and high energy density. Nevertheless, their practical applications remain constrained by the sluggish sulfur reaction kinetics. While catalytic strategies have been demonstrated to facilitate sulfur conversion, their efficacy is fundamentally constrained by the lack of interfacial continuity. Thus, there is an urgent need for interfacial fusion to achieve such continuity and construct efficient catalytic interfaces. In this work, an amorphous interfacial fusion strategy using TiS₂ as a catalytic "solder", enabling intimate integration among sulfur, the catalyst, and the solid-state electrolyte is proposed. Upon reacting with sulfur and the sulfide-based solid electrolyte, TiS₂ induces the in situ formation of amorphous TiS₄ and Li-Ti-P-S-Cl interfacial phases. These amorphous phases facilitate interfacial "soldering", creating integrated catalytic interfaces that enhance Li⁺ transport and catalytic efficiency. As a result, the optimized ASSLSBs show a reversible specific capacity of 720 mAh g^-1 after 2000 cycles at 1 C. It also delivers a high areal capacity of 7.05 mAh cm^-2 at a sulfur loading of 4.0 mg cm^-2. This interfacial fusion strategy offers a promising pathway toward the practical development of high-performance ASSLSBs.