Mechanically Induced Bridged Interlayer Enabling Highly Reversible All‐Solid‐State Sulfur Cathodes

All-solid-state lithium-sulfur batteries (ASSLSBs) show great promise for next-generation energy storage systems due to their high energy density, low cost, and enhanced safety features. However, constrained solid-state sulfur conversion severely limits their cycling stability and rate performance, presenting significant obstacles to industrial implementation. Here, a mechanochemical synthesis approach is developed that simultaneously addresses multiscale kinetic limitations of all-solid-state sulfur cathodes across molecular, interfacial, and electrode levels. The in situ generated amorphous lithium iodothiophosphate (LPSI) interlayer, chemically bridged between sulfur active materials and sulfide catholytes, establishes effective and durable Li-ion conduction pathways through reduced diffusion resistance and reinforced interfacial contact. Moreover, the LPSI functions as percolated redox mediators that modulate sulfur redox pathways and electrochemically activate sulfur species, facilitating rapid sulfur redox kinetics. The developed sulfur cathode (S@LPSI/LPSC) demonstrates exceptional electrochemical performance, maintaining 93.8% capacity retention, exceeding 1600 cycles at a high sulfur loading of 6 mg cm^-2 and an elevated current density of 5 mA cm^-2. Pouch cells incorporating the S@LPSI/LPSC cathode demonstrate gravimetric energy densities exceeding 420 Wh kg^-1. This work provides valuable insights into highly reversible all-solid-state sulfur cathodes, significantly advancing the industrialization of ASSLSB technology.