Insertion-dominated anion redox in high-capacity amorphous sulfide cathodes for solid-state batteries

Sulfide-based all-solid-state batteries (ASSBs) offer high-energy and safe energy storage, yet their performance remains limited by the structural instability of conventional crystalline cathodes and poor interfacial compatibility with sulfide solid electrolytes (SEs). Herein, we propose a synergistic cathode design integrating interfacial quasi-homogenization, structural amorphization, and anion-enrichment regulation, using titanium sulfides as a proof-of-concept system. This strategy enables insertion-dominated cation-anion multi-electron redox while promoting a chemically compatible interface and improved deformation accommodation, thereby maintaining interfacial contact during chemo-mechanical evolution and suppressing parasitic reactions. Without surface coatings or multilayer SE architectures, the selected TiS$_3$-based composite cathode delivers an ultrahigh capacity above 550 mAh g$^{−1}$, a specific energy exceeding 1,000 Wh kg$^{−1}$, and retains 390 mAh g$^{−1}$ over 2,800 cycles at 2.0 A g$^{−1}$ with ∼90% capacity retention, surpassing many reported layered oxide-based cathodes. This work bridges anion chemistry, structural disorder, and interfacial stability, offering a design principle for high-performance sulfide ASSBs.