High-Areal-Capacity Sulfur Cathode Enabled by Dual-Phase Electrolyte for Sulfide-Based All-Solid-State Batteries

All-solid-state lithium–sulfur batteries (ASSLSBs) incorporating sulfide-based superionic conductors offer high safety and energy density and are cost-efficient. However, the effective utilization of sulfur is challenging due to the difficulties in forming an intimate triple-phase interface between the electronic conductors, ionic conductors, and sulfur. In this study, high-performance ASSLSBs are achieved through a simple two-step mixing method that combines 1) high-energy ball milling and 2) mild mixing of a sulfur/carbon composite with Li₆PS₅Cl (LPSCl). This approach reduces the particle size, enhances the mixing uniformity, and activates the redox reaction of LPSCl while preserving its superionic conductivity, ultimately creating well-distributed conduction pathways in thick electrodes. During the milling, a catenation reaction between sulfur and LPSCl leads to the formation of inorganic Li-ion-conducting species, improving the ionic contact of sulfur. Moreover, the S–S bridging and cleavage reactions of the oxidatively decomposed LPSCl contribute reversibly to the additional capacity within the operating voltage range. Consequently, the optimal ASSLSB demonstrated a high areal capacity of 10.1 mAh cm⁻², retaining 92.0% of its initial capacity after 150 cycles at 30 °C. This cathode design is further extendable to other sulfur-based cathodes and dry electrode fabrication, offering a viable pathway toward practical high-energy ASSLSBs.