In Situ Solid Electrolyte Ionic Pathway Formation in High Sulfur Loading Cathodes for High‐Performance All‐Solid‐State Lithium–Sulfur Batteries

Abstract All‐solid‐state lithium–sulfur batteries (ASSLSBs) are promising for next‐generation energy storage. However, the limited ionic and electronic conductivities of sulfur‐based cathodes make them difficult to realize high sulfur content and high areal loading. Herein, a facile approach of in situ solid electrolyte formation is used to build ionic pathways in high sulfur loading cathodes. A precursor of P₂S₅ is introduced into the interior space of sulfur‐carbon secondary particles, and its in situ reaction with the discharge product Li₂S forms lithium phosphorus sulfide solid‐state electrolyte that establishes 3D ionic pathways within the cathodes. This approach not only activates more active materials but also boosts the overall ionic conductivity of the cathodes. The optimized cathode with a sulfur loading of 4 mg cm⁻² can achieve a high specific capacity of 1340 mAh g⁻¹ (based on sulfur mass) with 89% capacity retention after 100 cycles at 0.1C (1C = 1675 mA g⁻¹). Even with a higher sulfur loading of 8 mg cm⁻², the cathode still demonstrates a very high active materials utilization with an areal capacity of 9.2 mAh cm⁻². The simple and effective method to realize high‐performance sulfur cathode with built‐in solid electrolyte ionic pathways would be useful for the further development of practical ASSLSBs.